U.S. patent number 5,859,971 [Application Number 08/601,903] was granted by the patent office on 1999-01-12 for differencing client/server communication system for use with cgi forms.
This patent grant is currently assigned to International Business Machines Corp.. Invention is credited to Reed Reed Bittinger, Michael Levi Fraenkel, Barron Cornelius Housel III, David Bruce Lindquist.
United States Patent |
5,859,971 |
Bittinger , et al. |
January 12, 1999 |
Differencing client/server communication system for use with CGI
forms
Abstract
A method, apparatus and computer program product for reducing
the data transmitted over an external communication link from a
first application resident in a first computer to a second
application resident in a second computer. The method, apparatus
and computer program product include storing a data stream from the
first application to be provided to the second application in
response to a request from the second application in a cache
resident in the first computer to create a server base cache entry
and in a cache resident in the second computer to create a client
base cache entry. Requests from the second application are
interrogated to determine if a client base cache entry
corresponding to the interrogated request exists and to determine
if a server base cache entry corresponding to the interrogated
request exists. The response data stream is intercepted prior to
transmission of the response on the external communication link and
compared to the server base cache entry to provide difference data
corresponding to the difference between the intercepted response
and the server base cache entry. The difference data is sent over
the external communication link and acquired by the second computer
which reconstructs the response data stream by combining the client
base cache entry with the difference data to create a response data
stream which is provided to the second application.
Inventors: |
Bittinger; Reed Reed (Raleigh,
NC), Fraenkel; Michael Levi (Raleigh, NC), Housel III;
Barron Cornelius (Chapel Hill, NC), Lindquist; David
Bruce (Raleigh., NC) |
Assignee: |
International Business Machines
Corp. (Armonk, NY)
|
Family
ID: |
24409216 |
Appl.
No.: |
08/601,903 |
Filed: |
February 15, 1996 |
Current U.S.
Class: |
709/203;
707/E17.12; 709/218 |
Current CPC
Class: |
H04L
67/04 (20130101); H04L 67/2828 (20130101); H04L
67/2876 (20130101); H04L 29/06 (20130101); G06F
16/9574 (20190101); H04L 69/329 (20130101); H04L
67/142 (20130101); H04L 67/2852 (20130101); H04L
67/02 (20130101) |
Current International
Class: |
G06F
17/30 (20060101); H04L 29/06 (20060101); H04L
29/08 (20060101); G06F 003/00 () |
Field of
Search: |
;395/200.01,200.48,200.47,200.33,200 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
IBM Technical Disclosure Bulletin, Method to Reduce Changed Data
Sent Between Computer Systems, vol. 35, No. 1B, pp. 110-112. .
Austin, et al., File System Caching in Large Point-to-Point
Networks, Software Engineering Journal, vol. 7, No. 1, pp. 65-80
(Jan. 1992). .
Nelson, et al., Caching in the Sprite Network File System,
Operating Systems Review, vol. 21, No. 5, pp. 3-4 (1987). .
Huizinga, et al., Two-Level Client Caching and Disconnected
Operation of Notebook Computers in Distributed Systems, SIGICE
Bulletin, vol. 21, No. 1, pp. 9-14 (Jul. 1995). .
Abstract, IBM Technical Disclosure Bulletin, Method for
Transmitting Only Document Change Data, vol. 27, pp. 844-846 (Jun.
1984). .
International Search Report. .
Hyptertext Transfer Protocol--HTTP/1.0, HTTP Working Group,
Berners-Lee et al.--Internet-Draft Basic HTTP. .
IBM Sales Brochure G325-3598-0 printed Sep. 1995. .
IBM Sales Brochure G325-3595-00, printed Sep. 1995. .
IBM ARTour Technical Overview--Release 1. .
IBM Publication SB14-0110-00, 1995..
|
Primary Examiner: Lall; Parshotam S.
Assistant Examiner: Coulter; Kenneth R.
Attorney, Agent or Firm: Herndon; Jerry W.
Claims
That which is claimed is:
1. A method of reducing the data transmitted over a communication
link from a first application resident in a first computer and to a
second application resident in a second computer wherein the data
is transmitted over an external communication link from the first
computer to the second computer, the method comprising:
storing a data stream from the first application to be provided to
the second application in response to a CGI request from the second
application in a cache resident in the first computer to create a
server base cache entry;
storing a data stream to be provided to the second application in
response to a CGI request from the second application in a cache
resident in the second computer to create a client base cache
entry;
evaluating the requests from the second application to determine if
a client base cache entry corresponding to the interrogated request
exists to provide a client CGI base form;
interrogating requests from the second application to determine if
a server base cache entry corresponding to the interrogated request
exists to provide a server CGI base form;
intercepting the data stream corresponding to the response
originated by the first application in response to the interrogated
request from the second application prior to transmission of the
response on the external communication link;
comparing the intercepted response to the server CGI base form to
provide difference data corresponding to the difference between the
intercepted response and the server CGI base form;
sending the difference data to the second computer over the
external communication link;
acquiring the difference data transmitted over the external
communication link sent by the first computer;
reconstructing the response data stream corresponding to the
communication from the first application from the client/server
specific data stream received over the external communication link
by combining the client CGI base form with the difference data
received over the external communication link to create a response
data stream corresponding to the intercepted response;
selectively updating the client cache entry corresponding to the
client CGI base form so as to provide a new client CGI base form
wherein the CGI base form is updated with the received difference
data if an update criteria is met; and
providing the reconstructed data stream corresponding to the
intercepted response to the second application.
2. The method of claim 1 further comprising the steps of:
determining if the difference between the server base form and the
intercepted response is greater than a predefined difference
threshold;
updating the server base form corresponding to the interrogated
request by storing the intercepted response data stream received
from the first application as the server base cache entry
corresponding to the intercepted request if the difference between
the server base form and the intercepted response is greater than
the predefined difference threshold; and
wherein said comparing step and said sending step utilizes the
updated server base form.
3. The method of claim 1 wherein the first application comprises a
web server and the second application comprises a web browser.
4. The method of claim 1 wherein the external communication link
comprises a wireless communication link.
5. An apparatus for reducing the amount of data transmitted from a
first application resident in a first computer to a second
application resident in a second computer in response to a request
from the second application wherein the data is transmitted over an
external communication link from the first computer to the second
computer, the apparatus comprising:
means for storing a data stream from the first application to be
provided to the second application in response to a CGI request
from the second application in a cache resident in the first
computer to create a server base cache entry;
means for storing a data stream to be provided to the second
application in response to a CGI request from the second
application in a cache resident in the second computer to create a
client base cache entry;
means for evaluating the requests from the second application to
determine if a client base cache entry corresponding to the
interrogated request exists to provide a client CGI base form;
means for interrogating requests from the second application to
determine if a server base cache entry corresponding to the
interrogated request exists to provide a server CGI base form;
means for intercepting the data stream corresponding to the
response originated by the first application in response to the
interrogated request from the second application prior to
transmission of the response on the external communication
link;
means for comparing the intercepted response to the server CGI base
form to provide difference data corresponding to the difference
between the intercepted response and the server base form;
means for sending the difference data to the second computer over
the external communication link;
means for acquiring the difference data transmitted over the
external communication link sent by the first computer;
means for reconstructing the response data stream corresponding to
the communication from the first application from the client/server
specific data stream received over the external communication link
by combining the client CGI base form with the difference data
received over the external communication link to create a response
data stream corresponding to the intercepted response;
means for selectively updating the client cache entry corresponding
to the client CGI base form so as to provide a new client CGI base
form wherein the CGI base form is updated with the received
difference data if an update criteria is met; and
means for providing the reconstructed data stream corresponding to
the intercepted response to the second application.
6. The apparatus of claim 5 further comprising:
means for determining if the difference between the server base
form and the intercepted response is greater than a predefined
difference threshold;
means for updating the server base form corresponding to the
interrogated request by storing the intercepted response data
stream received from the first application as the server base cache
entry corresponding to the intercepted request if the difference
between the server base form and the intercepted response is
greater than the predefined difference threshold; and
wherein said means for comparing and said means for sending
utilizes the updated server base form.
7. The apparatus of claim 5 wherein the first application comprises
a web server and the second application comprises a web
browser.
8. The apparatus of claim 5 wherein the external communication link
comprises a wireless communication link.
9. A computer program product for reducing the amount of data
transmitted from a first application resident in a first computer
to a second application resident in a second computer in response
to a request from the second application wherein the data is
transmitted over an external communication link from the first
computer to the second computer, the computer program product
comprising:
a computer-readable storage medium having computer-readable program
code means embodied in said medium, said computer-readable program
code means comprising:
computer readable program code means for storing a data stream from
the first application to be provided to the second application in
response to a CGI request from the second application in a cache
resident in the first computer to create a server base cache
entry;
computer readable program code means for storing a data stream to
be provided to the second application in response to a CGI request
from the second application in a cache resident in the second
computer to create a client base cache entry;
computer readable program code means for evaluating the requests
from the second application to determine if a client base cache
entry corresponding to the interrogated request exists to provide a
client CGI base form;
computer readable program code means for interrogating requests
from the second application to determine if a server base cache
entry corresponding to the interrogated request exists to provide a
server CGI base form;
computer readable program code means for intercepting the data
stream corresponding to the response originated by the first
application in response to the interrogated request from the second
application prior to transmission of the response on the external
communication link;
computer readable program code means for comparing the intercepted
response to the server base form to provide difference data
corresponding to the difference between the intercepted response
and the server CGI base form;
computer readable program code means for sending the difference
data to the second computer over the external communication
link;
computer readable program code means for acquiring the difference
data transmitted over the external communication link sent by the
first computer; computer readable program code means for
reconstructing the response data stream corresponding to the
communication from the first application from the client/server
specific data stream received over the external communication link
by combining the client CGI base form with the difference data
received over the external communication link to create a response
data stream corresponding to the intercepted response;
computer readable program code means for selectively updating the
client cache entry corresponding to the client CGI base form so as
to provide a new client CGI base form wherein the CGI base form is
updated with the received difference data if an update criteria is
met; and
computer readable program code means for providing the
reconstructed data stream corresponding to the intercepted response
to the second application.
10. The computer program product of claim 9 further comprising:
computer readable program code means for determining if the
difference between the server base form and the intercepted
response is greater than a predefined difference threshold;
computer readable program code means for updating the server base
form corresponding to the interrogated request by storing the
intercepted response data stream received from the first
application as the server base cache entry corresponding to the
intercepted request if the difference between the server base form
and the intercepted response is greater than the predefined
difference threshold; and
wherein said computer readable program code means for comparing and
said computer readable program code means for sending utilizes the
updated server base form.
11. The computer program product of claim 9 wherein the first
application comprises a web server and the second application
comprises a web browser.
12. The apparatus of claim 9 wherein the external communication
link comprises a wireless communication link.
13. A method of reducing the data transmitted over a communication
link from a first application resident in a first computer and to a
second application resident in a second computer wherein the data
is transmitted over an external communication link from the first
computer to the second computer, the method comprising:
storing a data stream from the first application to be provided to
the second application in response to a request from the second
application in a cache resident in the first computer to create a
server base cache entry;
storing a data stream to be provided to the second application in
response to a request from the second application in a cache
resident in the second computer to create a client base cache
entry;
evaluating the requests from the second application to determine if
a client base cache entry corresponding to the interrogated request
exists to provide a client base form;
interrogating requests from the second application to determine if
a server base cache entry corresponding to the interrogated request
exists to provide a server base form;
intercepting the data stream corresponding to the response
originated by the first application in response to the interrogated
request from the second application prior to transmission of the
response on the external communication link;
comparing the intercepted response to the server base form to
provide difference data corresponding to the difference between the
intercepted response and the server base form;
sending the difference data to the second computer over the
external communication link;
acquiring the difference data transmitted over the external
communication link sent by the first computer;
providing the reconstructed data stream corresponding to the
intercepted response to the second application,
determining if the server base form is identical to the client base
form;
transmitting the server base form to the second computer over the
external communication link if the server base form is not
identical to the client base form;
reconstructing the response data stream corresponding to the
communication from the first application from the client/server
specific data stream received over the external communication link
by combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response if the server base
form is not transmitted to the second computer and reconstructing
the intercepted response data stream corresponding to the response
from the first application by combining the server base form
received over the external communication link with the difference
data received over the external communication link to create a data
stream corresponding to the intercepted response if the server base
form is transmitted to the second computer; and
updating the client base form corresponding to the interrogated
request by storing the received server base form as the client base
cache entry corresponding to the interrogated request.
14. The method of claim 13 further comprising the steps of:
determining if the difference between the server base form and the
intercepted response is greater than a predefined difference
threshold;
updating the server base form corresponding to the interrogated
request by storing the intercepted response data stream received
from the first application as the server base cache entry
corresponding to the intercepted request if the difference between
the server base form and the intercepted response is greater than
the predefined difference threshold; and
wherein said comparing step and said sending step utilizes the
updated server base form.
15. The method of claim 13 further comprising the steps of:
maintaining a plurality of server base cache entries which
correspond to the request from the second application;
wherein said interrogating step comprises determining if a
plurality of server base cache entries exist corresponding to the
request from the second application to provide a plurality of
server base forms;
determining if one of the plurality of server base forms is
identical to the client base form; and
wherein said comparing step utilizes the one of the plurality of
server base forms which is identical to the client base form if
said determining step determines that one of the plurality of
server base forms is identical to the client base form.
16. The method of claim 13 further comprising the steps of:
updating the server cache entry with the data stream from the first
application in response to the request from the second
application;
maintaining a plurality of difference data sets which correspond to
the request from the second application and which represent the
differences between successive server cache entries to provide
archival difference data;
maintaining a plurality of CRC entries wherein each of said
plurality of CRC entries is associated with one of said plurality
of difference data sets and uniquely identify the server base form
from which said difference data set was derived;
wherein said interrogating step comprises determining if a
plurality of difference data sets and CRCs exist corresponding to
the request from the second application;
determining if one of said plurality of CRCs is corresponds to a
server base form which is identical to the client base form;
wherein said sending step comprises sending the archival difference
data corresponding to the CRC which corresponds to the client base
form the successive archival difference data sets and the
difference data calculated by said comparing step to the second
computer over the external communication link;
wherein said reconstructing step comprises reconstructing the
response data stream corresponding to the communication from the
first application from the data stream received over the external
communication link by successively combining the client base form
with the difference data received over the external communication
link to create a response data stream corresponding to the
intercepted response;
updating the client cache entry corresponding to the request from
the second application with the reconstructed data stream.
17. The method of claim 13 wherein the first application comprises
a web server and the second application comprises a web
browser.
18. The method of claim 13 wherein the external communication link
comprises a wireless communication link.
19. The method of claim 17 wherein the request from the web browser
comprises a CGI request.
20. An apparatus for reducing the data transmitted over a
communication link from a first application resident in a first
computer and to a second application resident in a second computer
wherein the data is transmitted over an external communication link
from the first computer to the second computer, comprising:
means for storing a data stream from the first application to be
provided to the second application in response to a request from
the second application in a cache resident in the first computer to
create a server base cache entry;
means for storing a data stream to be provided to the second
application in response to a request from the second application in
a cache resident in the second computer to create a client base
cache entry;
means for evaluating the requests from the second application to
determine if a client base cache entry corresponding to the
interrogated request exists to provide a client base form;
means for interrogating requests from the second application to
determine if a server base cache entry corresponding to the
interrogated request exists to provide a server base form;
means for intercepting the data stream corresponding to the
response originated by the first application in response to the
interrogated request from the second application prior to
transmission of the response on the external communication
link;
means for comparing the intercepted response to the server base
form to provide difference data corresponding to the difference
between the intercepted response and the server base form;
means for sending the difference data to the second computer over
the external communication link;
means for acquiring the difference data transmitted over the
external communication link sent by the first computer;
means for providing the reconstructed data stream corresponding to
the intercepted response to the second application;
means for determining if the server base form is identical to the
client base form;
means for transmitting the server base form to the second computer
over the external communication link if the server base form is not
identical to the client base form;
means for reconstructing the response data stream corresponding to
the communication from the first application from the client/server
specific data stream received over the external communication link
by combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response if the server base
form is not transmitted to the second computer and for
reconstructing the intercepted response data stream corresponding
to the response from the first application by combining the server
base form received over the external communication link with the
difference data received over the external communication link to
create a data stream corresponding to the intercepted response if
the server base form is transmitted to the second computer; and
means for updating the client base form corresponding to the
interrogated request by storing the received server base form as
the client base cache entry corresponding to the interrogated
request.
21. The apparatus of claim 20 further comprising:
means for determining if the difference between the server base
form and the intercepted response is greater than a predefined
difference threshold;
means for updating the server base form corresponding to the
interrogated request by storing the intercepted response data
stream received from the first application as the server base cache
entry corresponding to the intercepted request if the difference
between the server base form and the intercepted response is
greater than the predefined difference threshold; and
wherein said means for comparing and said means for sending
utilizes the updated server base form.
22. The apparatus of claim 20 further comprising:
means for maintaining a plurality of server base cache entries
which correspond to the request from the second application;
wherein said means for interrogating comprises means for
ascertaining if a plurality of sever base cache entries exist
corresponding to the request from the second application to provide
a plurality of server base forms;
means for determining if one of the plurality of server base forms
is identical to the client base form; and
wherein said means for comparing utilizes the one of the plurality
of server base forms which is identical to the client base form if
said means for determining determines that one of the plurality of
server base forms is identical to the client base form.
23. The apparatus of claim 20 further comprising:
means f6r updating the server cache entry with the data stream from
the first application in response to the request from the second
application;
means for maintaining a plurality of difference data sets which
correspond to the request from the second application and which
represent the differences between successive server cache entries
to provide archival difference data;
means for maintaining a plurality of CRC entries wherein each of
said plurality of CRC entries is associated with one of said
plurality of difference data sets and uniquely identify the server
base form from which said difference data set was derived;
wherein said means for interrogating comprises means for
determining if a plurality of difference data sets and CRCs exist
corresponding to the request from the second application;
means for determining if one of said plurality of CRCs is
corresponds to a server base form which is identical to the client
base form;
wherein said means for sending comprises means for sending the
archival difference data corresponding to the CRC which corresponds
to the client base form the successive archival difference data
sets and the difference data calculated by said means for comparing
to the second computer over the external communication link;
wherein said means for reconstructing comprises means for
reconstructing the response data stream corresponding to the
communication from the first application from the data stream
received over the external communication link by successively
combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response; and
means for updating the client cache entry corresponding to the
request from the second application with the reconstructed data
stream.
24. The apparatus of claim 20 wherein the first application
comprises a web server and the second application comprises a web
browser.
25. The apparatus of claim 20 wherein the external communication
link comprises a wireless communication link.
26. The apparatus of claim 24 wherein the request from the web
browser comprises a CGI request.
27. A computer program product for reducing the data transmitted
over a communication link from a first application resident in a
first computer and to a second application resident in a second
computer wherein the data is transmitted over an external
communication link from the first computer to the second computer,
comprising:
a computer-readable storage medium having computer-readable program
code means embodied in said medium, said computer-readable program
code means comprising:
computer readable program code means for storing a data stream from
the first application to be provided to the second application in
response to a request from the second application in a cache
resident in the first computer to create a server base cache
entry;
computer readable program code means for storing a data stream to
be provided to the second application in response to a request from
the second application in a cache resident in the second computer
to create a client base cache entry;
computer readable program code means for evaluating the requests
from the second application to determine if a client base cache
entry corresponding to the interrogated request exists to provide a
client base form;
computer readable program code means for interrogating requests
from the second application to determine if a server base cache
entry corresponding to the interrogated request exists to provide a
server base form;
computer readable program code means for intercepting the data
stream corresponding to the response originated by the first
application in response to the interrogated request from the second
application prior to transmission of the response on the external
communication link;
computer readable program code means for comparing the intercepted
response to the server base form to provide difference data
corresponding to the difference between the intercepted response
and the server base form;
computer readable program code means for sending the difference
data to the second computer over the external communication
link;
computer readable program code means for acquiring the difference
data transmitted over the external communication link sent by the
first computer;
computer readable program code means for providing the
reconstructed data stream corresponding to the intercepted response
to the second application. computer readable program code means for
determining if the server base form is identical to the client base
form;
computer readable program code means for transmitting the server
base form to the second computer over the external communication
link if the server base form is not identical to the client base
form;
computer readable program code means for reconstructing the
response data stream corresponding to the communication from the
first application from the client/server specific data stream
received over the external communication link by combining the
client base form with the difference data received over the
external communication link to create a response data stream
corresponding to the intercepted response if the server base form
is not transmitted to the second computer and for reconstructing
the intercepted response data stream corresponding to the response
from the first application by combining the server base form
received over the external communication link with the difference
data received over the external communication link to create a data
stream corresponding to the intercepted response if the server base
form is transmitted to the second computer; and
computer readable program code means for updating the client base
form corresponding to the interrogated request by storing the
received server base form as the client base cache entry
corresponding to the interrogated request.
28. The computer program product of claim 27 further
comprising:
computer readable program code means for determining if the
difference between the server base form and the intercepted
response is greater than a predefined difference threshold;
computer readable program code means for updating the server base
form corresponding to the interrogated request by storing the
intercepted response data stream received from the first
application as the server base cache entry corresponding to the
intercepted request if the difference between the server base form
and the intercepted response is greater than the predefined
difference threshold; and
wherein said computer readable program code means for comparing and
said computer readable program code means for sending utilizes the
updated server base form.
29. The computer program product of claim 27 further
comprising:
computer readable program code means for maintaining a plurality of
server base cache entries which correspond to the request from the
second application;
wherein said computer readable program code means for interrogating
comprises computer readable program code means for ascertaining if
a plurality of sever base cache entries exist corresponding to the
request from the second application to provide a plurality of
server base forms;
computer readable program code means for determining if one of the
plurality of server base forms is identical to the client base
form; and
wherein said computer readable program code means for comparing
utilizes the one of the plurality of server base forms which is
identical to the client base form if said computer readable program
code means for determining determines that one of the plurality of
server base forms is identical to the client base form.
30. The computer program product of claim 27 further
comprising:
computer readable program code means for updating the server cache
entry with the data stream from the first application in response
to the request from the second application;
computer readable program code means for maintaining a plurality of
difference data sets which correspond to the request from the
second application and which represent the differences between
successive server cache entries to provide archival difference
data;
computer readable program code means for maintaining a plurality of
CRC entries wherein each of said plurality of CRC entries is
associated with one of said plurality of difference data sets and
uniquely identify the server base form from which said difference
data set was derived;
wherein said computer readable program code means for interrogating
comprises computer readable program code means for determining if a
plurality of difference data sets and CRCs exist corresponding to
the request from the second application;
computer readable program code means for determining if one of said
plurality of CRCs is corresponds to a server base form which is
identical to the client base form;
wherein said computer readable program code means for sending
comprises computer readable program code means for sending the
archival difference data corresponding to the CRC which corresponds
to the client base form the successive archival difference data
sets and the difference data calculated by said computer readable
program code means for comparing to the second computer over the
external communication link;
wherein said computer readable program code means for
reconstructing comprises computer readable program code means for
reconstructing the response data stream corresponding to the
communication from the first application from the data stream
received over the external communication link by successively
combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response; and
computer readable program code means for updating the client cache
entry corresponding to the request from the second application with
the reconstructed data stream.
31. The computer program product of claim 27 wherein the first
application comprises a web server and the second application
comprises a web browser.
32. The computer program product of claim 27 wherein the external
communication link comprises a wireless communication link.
33. The computer program product of claim 31 wherein the request
from the web browser comprises a CGI request.
34. A method of reducing the data transmitted over a communication
link from a first application resident in a first computer and to a
second application resident in a second computer wherein the data
is transmitted over an external communication link from the first
computer to the second computer, the method comprising:
storing a plurality of data stream from the first application to be
provided to the second application corresponding to a request from
the second application in a cache resident in the first computer to
create a plurality of server base cache entries;
storing a data stream to be provided to the second application in
response to a request from the second application in a cache
resident in the second computer to create a client base cache
entry;
evaluating the requests from the second application to determine if
a client base cache entry corresponding to the interrogated request
exists to provide a client base form;
interrogating requests from the second application to determine if
a plurality of server base cache entries corresponding to the
interrogated request exist to provide a plurality of server base
forms;
determining if one of the plurality of server base forms is
identical to the client base form;
intercepting the data stream corresponding to the response
originated by the first application in response to the interrogated
request from the second application prior to transmission of the
response on the external communication link;
comparing the intercepted response to the one of the plurality of
server base forms which is identical to the client base form to
provide difference data corresponding to the difference between the
intercepted response and the server base form;
sending the difference data to the second computer over the
external communication link;
acquiring the difference data transmitted over the external
communication link sent by the first computer;
reconstructing the response data stream corresponding to the
communication from the first application from the client/server
specific data stream received over the external communication link
by combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response; and
providing the reconstructed data stream corresponding to the
intercepted response to the second application.
35. The method of claim 34 further comprising the steps of:
determining if the difference between the server base form and the
intercepted response is greater than a predefined difference
threshold;
updating the server base form corresponding to the interrogated
request by storing the intercepted response data stream received
from the first application as the server base cache entry
corresponding to the intercepted request if the difference between
the server base form and the intercepted response is greater than
the predefined difference threshold; and
wherein said comparing step and said sending step utilizes the
updated server base form.
36. The method of claim 34 further comprising the steps of:
updating the server cache entry with the data stream from the first
application in response to the request from the second
application;
maintaining a plurality of difference data sets which correspond to
the request from the second application and which represent the
differences between successive server cache entries to provide
archival difference data;
maintaining a plurality of CRC entries wherein each of said
plurality of CRC entries is associated with one of said plurality
of difference data sets and uniquely identify the server base form
from which said difference data set was derived;
wherein said interrogating step comprises determining if a
plurality of difference data sets and CRCs exist corresponding to
the request from the second application;
determining if one of said plurality of CRCs is corresponds to a
server base form which is identical to the client base form;
wherein said sending step comprises sending the archival difference
data corresponding to the CRC which corresponds to the client base
form the successive archival difference data sets and the
difference data calculated by said comparing step to the second
computer over the external communication link;
wherein said reconstructing step comprises reconstructing the
response data stream corresponding to the communication from the
first application from the data stream received over the external
communication link by successively combining the client base form
with the difference data received over the external communication
link to create a response data stream corresponding to the
intercepted response;
updating the client cache entry corresponding to the request from
the second application with the reconstructed data stream.
37. An apparatus for reducing the data transmitted over a
communication link from a first application resident in a first
computer and to a second application resident in a second computer
wherein the data is transmitted over an external communication link
from the first computer to the second computer, comprising:
means for storing a plurality of data stream from the first
application to be provided to the second application corresponding
to a request from the second application in a cache resident in the
first computer to create a plurality of server base cache
entries;
means for storing a data stream to be provided to the second
application in response to a request from the second application in
a cache resident in the second computer to create a client base
cache entry;
means for evaluating the requests from the second application to
determine if a client base cache entry corresponding to the
interrogated request exists to provide a client base form;
means for interrogating requests from the second application to
determine if a plurality of server base cache entries corresponding
to the interrogated request exist to provide a plurality of server
base forms;
means for determining if one of the plurality of server base forms
is identical to the client base form;
means for intercepting the data stream corresponding to the
response originated by the first application in response to the
interrogated request from the second application prior to
transmission of the response on the external communication
link;
means for comparing the intercepted response to the one of the
plurality of server base forms which is identical to the client
base form to provide difference data corresponding to the
difference between the intercepted response and the server base
form;
means for sending the difference data to the second computer over
the external communication link;
means for acquiring the difference data transmitted over the
external communication link sent by the first computer;
means for reconstructing the response data stream corresponding to
the communication from the first application from the client/server
specific data stream received over the external communication link
by combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response; and
means for providing the reconstructed data stream corresponding to
the intercepted response to the second application.
38. The apparatus of claim 37 further comprising:
means for determining if the difference between the server base
form and the intercepted response is greater than a predefined
difference threshold;
means for updating the server base form corresponding to the
interrogated request by storing the intercepted response data
stream received from the first application as the server base cache
entry corresponding to the intercepted request if the difference
between the server base form and the intercepted response is
greater than the predefined difference threshold; and
wherein said means for comparing and said means for sending
utilizes the updated server base form.
39. The apparatus of claim 37 further comprising:
means for updating the server cache entry with the data stream from
the first application in response to the request from the second
application;
means for maintaining a plurality of difference data sets which
correspond to the request from the second application and which
represent the differences between successive server cache entries
to provide archival difference data;
means for maintaining a plurality of CRC entries wherein each of
said plurality of CRC entries is associated with one of said
plurality of difference data sets and uniquely identify the server
base form from which said difference data set was derived;
wherein said means for interrogating comprises means for
determining if a plurality of difference data sets and CRCs exist
corresponding to the request from the second application;
means for determining if one of said plurality of CRCs is
corresponds to a server base form which is identical to the client
base form;
wherein said means for sending comprises means for sending the
archival difference data corresponding to the CRC which corresponds
to the client base form the successive archival difference data
sets and the difference data calculated by said means for comparing
to the second computer over the external communication link;
wherein said means for reconstructing comprises means for
reconstructing the response data stream corresponding to the
communication from the first application from the data stream
received over the external communication link by successively
combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response; and
means for updating the client cache entry corresponding to the
request from the second application with the reconstructed data
stream.
40. A computer program product for reducing the data transmitted
over a communication link from a first application resident in a
first computer and to a second application resident in a second
computer wherein the data is transmitted over an external
communication link from the first computer to the second computer,
comprising:
a computer-readable storage medium having computer-readable program
code means embodied in said medium, said computer-readable program
code means comprising:
computer readable program code means for storing a plurality of
data stream from the first application to be provided to the second
application corresponding to a request from the second application
in a cache resident in the first computer to create a plurality of
server base cache entries;
computer readable program code means for storing a data stream to
be provided to the second application in response to a request from
the second application in a cache resident in the second computer
to create a client base cache entry;
computer readable program code means for evaluating the requests
from the second application to determine if a client base cache
entry corresponding to the interrogated request exists to provide a
client base form;
computer readable program code means for interrogating requests
from the second application to determine if a plurality of server
base cache entries corresponding to the interrogated request exist
to provide a plurality of server base forms;
computer readable program code means for determining if one of the
plurality of server base forms is identical to the client base
form;
computer readable program code means for intercepting the data
stream corresponding to the response originated by the first
application in response to the interrogated request from the second
application prior to transmission of the response on the external
communication link;
computer readable program code means for comparing the intercepted
response to the one of the plurality of server base forms which is
identical to the client base form to provide difference data
corresponding to the difference between the intercepted response
and the server base form;
computer readable program code means for sending the difference
data to the second computer over the external communication
link;
computer readable program code means for acquiring the difference
data transmitted over the external communication link sent by the
first computer;
computer readable program code means for reconstructing the
response data stream corresponding to the communication from the
first application from the client/server specific data stream
received over the external communication link by combining the
client base form with the difference data received over the
external communication link to create a response data stream
corresponding to the intercepted response; and
computer readable program code means for providing the
reconstructed data stream corresponding to the intercepted response
to the second application.
41. The computer program product of claim 40 further
comprising:
computer readable program code means for determining if the
difference between the server base form and the intercepted
response is greater than a predefined difference threshold;
computer readable program code means for updating the server base
form corresponding to the interrogated request by storing the
intercepted response data stream received from the first
application as the server base cache entry corresponding to the
intercepted request if the difference between the server base form
and the intercepted response is greater than the predefined
difference threshold; and
wherein said computer readable program code means for comparing and
said computer readable program code means for sending utilizes the
updated server base form.
42. The computer program product of claim 40 further
comprising:
computer readable program code means for updating the server cache
entry with the data stream from the first application in response
to the request from the second application;
computer readable program code means for maintaining a plurality of
difference data sets which correspond to the request from the
second application and which represent the differences between
successive server cache entries to provide archival difference
data;
computer readable program code means for maintaining a plurality of
CRC entries wherein each of said plurality of CRC entries is
associated with one of said plurality of difference data sets and
uniquely identify the server base form from which said difference
data set was derived;
wherein said computer readable program code means for interrogating
comprises computer readable program code means for determining if a
plurality of difference data sets and CRCs exist corresponding to
the request from the second application;
computer readable program code means for determining if one of said
plurality of CRCs is corresponds to a server base form which is
identical to the client base form;
wherein said computer readable program code means for sending
comprises computer readable program code means for sending the
archival difference data corresponding to the CRC which corresponds
to the client base form the successive archival difference data
sets and the difference data calculated by said computer readable
program code means for comparing to the second computer over the
external communication link;
wherein said computer readable program code means for
reconstructing comprises computer readable program code means for
reconstructing the response data stream corresponding to the
communication from the first application from the data stream
received over the external communication link by successively
combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response; and
computer readable program code means for updating the client cache
entry corresponding to the request from the second application with
the reconstructed data stream.
43. A method of reducing the data transmitted over an external
communication link from a first application resident in a first
computer to a second application resident in a second computer, the
method comprising:
storing a data stream from the first application to be provided to
the second application in response to a request from the second
application in a cache resident in the first computer to create a
server base cache entry;
storing a data stream to be provided to the second application in
response to a request from the second application in a cache
resident in the second computer to create a client base cache
entry;
evaluating the requests from the second application to determine if
a client base cache entry corresponding to the interrogated request
exists to provide a client base form;
maintaining a plurality of difference data sets which correspond to
the request from the second application and which represent the
differences between successive server cache entries to provide
archival difference data;
maintaining a plurality of CRC entries wherein each of said
plurality of CRC entries is associated with one of said plurality
of difference data sets and uniquely identify the server base form
from which said difference data set was derived;
interrogating requests from the second application to determine if
a plurality of difference data sets and CRCs exist corresponding to
the request from the second application;
determining if one of said plurality of CRCs is corresponds to a
server base form which is identical to the client base form;
intercepting the data stream corresponding to the response
originated by the first application in response to the interrogated
request from the second application prior to transmission of the
response on the external communication link;
comparing the intercepted response to the server base form to
provide difference data corresponding to the difference between the
intercepted response and the server base form;
updating the server cache entry with the data stream from the first
application in response to the request from the second
application;
sending the archival difference data corresponding to the CRC which
corresponds to the client base form, the successive archival
difference data sets and the difference data calculated by said
comparing step to the second application over the external
communication link;
acquiring the difference data from the external communication
link;
reconstructing the response data stream corresponding to the
communication from the first application by successively combining
the client base form with the acquired difference data to create a
response data stream corresponding to the intercepted response;
updating the client cache entry corresponding to the request from
the second application with the reconstructed data stream; and
providing the reconstructed data stream corresponding to the
intercepted response to the second application.
44. The method of claim 43 further comprising the steps of:
determining if the difference between the server base form and the
intercepted response is greater than a predefined difference
threshold;
updating the server base form corresponding to the interrogated
request by storing the intercepted response data stream received
from the first application as the server base cache entry
corresponding to the intercepted request if the difference between
the server base form and the intercepted response is greater than
the predefined difference threshold; and
wherein said comparing step and said sending step utilizes the
updated server base form.
45. An apparatus for reducing the data transmitted over an external
communication link from a first application resident in a first
computer to a second application resident in a second computer,
comprising:
means for storing a data stream from the first application to be
provided to the second application in response to a request from
the second application in a cache resident in the first computer to
create a server base cache entry;
means for storing a data stream to be provided to the second
application in response to a request from the second application in
a cache resident in the second computer to create a client base
cache entry;
means for evaluating the requests from the second application to
determine if a client base cache entry corresponding to the
interrogated request exists to provide a client base form;
means for maintaining a plurality of difference data sets which
correspond to the request from the second application and which
represent the differences between successive server cache entries
to provide archival difference data;
means for maintaining a plurality of CRC entries wherein each of
said plurality of CRC entries is associated with one of said
plurality of difference data sets and uniquely identify the server
base form from which said difference data set was derived;
means for interrogating requests from the second application to
determine if a plurality of difference data sets and CRCs exist
corresponding to the request from the second application;
means for determining if one of said plurality of CRCs is
corresponds to a server base form which is identical to the client
base form;
means for intercepting the data stream corresponding to the
response originated by the first application in response to the
interrogated request from the second application prior to
transmission of the response on the external communication
link;
means for comparing the intercepted response to the server base
form to provide difference data corresponding to the difference
between the intercepted response and the server base form;
means for updating the server cache entry with the data stream from
the first application in response to the request from the second
application;
means for sending the archival difference data corresponding to the
CRC which corresponds to the client base form, the successive
archival difference data sets and the difference data calculated by
said comparing step to the second application over the external
communication link;
means for acquiring the difference data from the external
communication link;
means for reconstructing the response data stream corresponding to
the communication from the first application by successively
combining the client base form with the acquired difference data to
create a response data stream corresponding to the intercepted
response;
means for updating the client cache entry corresponding to the
request from the second application with the reconstructed data
stream; and
means for providing the reconstructed data stream corresponding to
the intercepted response to the second application.
46. The apparatus of claim 45 further comprising:
means for determining if the difference between the server base
form and the intercepted response is greater than a predefined
difference threshold;
means for updating the server base form corresponding to the
interrogated request by storing the intercepted response data
stream received from the first application as the server base cache
entry corresponding to the intercepted request if the difference
between the server base form and the intercepted response is
greater than the predefined difference threshold; and
wherein said means for comparing and said means for sending
utilizes the updated server base form.
47. A computer program product for reducing the data transmitted
over an external communication link from a first application
resident in a first computer to a second application resident in a
second computer, the computer program product comprising:
a computer-readable storage medium having computer-readable program
code means embodied in said medium, said computer-readable program
code means comprising:
computer readable program code means for storing a data stream from
the first application to be provided to the second application in
response to a request from the second application in a cache
resident in the first computer to create a server base cache
entry;
computer readable program code means for storing a data stream to
be provided to the second application in response to a request from
the second application in a cache resident in the second computer
to create a client base cache entry;
computer readable program code means for evaluating the requests
from the second application to determine if a client base cache
entry corresponding to the interrogated request exists to provide a
client base form;
computer readable program code means for maintaining a plurality of
difference data sets which correspond to the request from the
second application and which represent the differences between
successive server cache entries to provide archival difference
data;
computer readable program code means for maintaining a plurality of
CRC entries wherein each of said plurality of CRC entries is
associated with one of said plurality of difference data sets and
uniquely identify the server base form from which said difference
data set was derived;
computer readable program code means for interrogating requests
from the second application to determine if a plurality of
difference data sets and CRCs exist corresponding to the request
from the second application;
computer readable program code means for determining if one of said
plurality of CRCs is corresponds to a server base form which is
identical to the client base form;
computer readable program code means for intercepting the data
stream corresponding to the response originated by the first
application in response to the interrogated request from the second
application prior to transmission of the response on the external
communication link;
computer readable program code means for comparing the intercepted
response to the server base form to provide difference data
corresponding to the difference between the intercepted response
and the server base form;
computer readable program code means for updating the server cache
entry with the data stream from the first application in response
to the request from the second application;
computer readable program code means for sending the archival
difference data corresponding to the CRC which corresponds to the
client base form, the successive archival difference data sets and
the difference data calculated by said comparing step to the second
application over the external communication link;
computer readable program code means for acquiring the difference
data from the external communication link;
computer readable program code means for reconstructing the
response data stream corresponding to the communication from the
first application by successively combining the client base form
with the acquired difference data to create a response data stream
corresponding to the intercepted response;
computer readable program code means for updating the client cache
entry corresponding to the request from the second application with
the reconstructed data stream; and
computer readable program code means for providing the
reconstructed data stream corresponding to the intercepted response
to the second application.
48. The computer program product of claim 47 further
comprising:
computer readable program code means for determining if the
difference between the server base form and the intercepted
response is greater than a predefined difference threshold;
computer readable program code means for updating the server base
form corresponding to the interrogated request by storing the
intercepted response data stream received from the first
application as the server base cache entry corresponding to the
intercepted request if the difference between the server base form
and the intercepted response is greater than the predefined
difference threshold; and
wherein said computer readable program code means for comparing and
said computer readable program code means for sending utilizes the
updated server base form.
Description
FIELD OF THE INVENTION
The present invention relates to methods of communicating between
applications resident on different computers such as a web browser
and a web server. More particularly the present invention relates
to differencing methods of communication over an external
communication link between two computers.
BACKGROUND OF THE INVENTION
The recent publicity and emphasis on the "information superhighway"
has increased awareness and acceptance of the Internet as a mass
communication media. This broad based recognition of the Internet
as a viable media for communication and interaction across multiple
networks has also created a large established user base built upon
the Internet standardized protocols for interaction between
computer networks.
The paradigm for the Internet is that of a client-server
relationship where Internet clients (browsers) communicate with
Internet servers. To provide greater access to the Internet the
communication protocols and languages utilized by the clients and
servers have become standardized. These protocols include the
Hyper-Text Transfer Protocol (HTTP), which is the communication
protocol used for communications between clients and servers, and
the Transfer Control Protocol/Internet Protocol (TCP/IP) the TCP
portion of which is the transport specific protocol for
communication between computers or applications. Also standardized
is the language in which clients and servers communicate which is
called Hyper-Text Markup Language (HTML). Because these protocols
and language are machine independent, and utilize a connectionless
best-efforts protocol to sending information, each transaction is
fully self contained. Thus, for example, each message from a client
contains information about the capabilities of the browser and is
independent of any other communications for the communication to be
completed. This self-contained nature of the communications between
a client and a server may be referred to as "stateless"
communications and increases the amount of data which must be
transferred between a client and a server for a given
communication.
In the context of the World Wide Web client/server applications the
client may be a web browser which acts as the user interface. The
web browser sends user requests to the appropriate web server and
formats and displays the HTML data returned from the web server.
The web browser also evaluates the HTML data to determine if there
are any embedded hyper-link statements in the HTML data which would
require subsequent browser requests which would then be initiated
by the browser. A web server acts as the server for the client and
processes the web browsers requests and returns the requested
response as an HTML data portion of a HTTP data stream.
As an example of a typical world wide web communication the case of
a web browser initiating a request for a "home page" from the web
server illustrates the basic relationship between HTTP, HTML, TCP
and the web browser and server. When the user of the web browser
requests information from a specific web site, the web browser
initiates communication with the web server by sending a "get"
request to the web server specifying the Universal Resource Locator
(URL) of the desired web site which, for purposes of this example,
may be a "home page." The URL acts as the address of the web site
and is unique throughout the Internet. The web server would then
obtain and supply the web browser with the HTML data corresponding
to the home page specified by the URL. This operation may involve
further communications on the Internet by the Internet web server
or the URL may specify the server which is in the local network to
which the browser is attached. The web browser would then evaluate
the HTML data received as an HTTP data stream from the web server
to see if there were any embedded hyper-links such as an icon or an
image and, if such a hyper-link exists would initiate requests
specifying the URL of the hyper-link to obtain the specified data.
This data would then be incorporated into the home page and
displayed to the user. As is seen in this simple example, a single
user input request by a web browser may result in multiple
additional requests which are automatically carried out by the web
browser in response to the receipt of the HTML data corresponding
to the user input request.
The basic communication structure for an Internet based system is
depicted in FIG. 1. In FIG. 1 a web browser 10 communicates with a
web server 20 over a communication link 15. This communication link
is typically a local area network connection, wide area network
connection, a connection over telephone lines or a combination
thereof. The web browser 10 communicates with the web server 20
using TCP/IP. For the majority of Internet communications a web
browser communicates with a web server using the generic
communication protocol HTTP which is transmitted between the web
browser and the web server over the TCP/IP link between the web
browser and the web server. The actual data transferred between the
web browser 10 and the web server 20 are HTTP data objects (e.g.
HTML data) as described above. The web server 20 may be a proxy
which receives web browser communications from a number of web
browsers and routes them to the appropriate server.
The popularity of the web browser/web server and their common
information and transport protocols, HTML and HTTP, has lead to
rapid acceptance of web technology as a universal interface for
network access to information. Furthermore, because the protocols
and language for communication between web browsers and web servers
are standardized the communication protocols and language will be
the same whether a user is using Netscape Navigator.TM., NCSA
Mosaic.TM., WebExplorer.TM. or any other web browser as their web
browser to access network information. Therefore, the large
installed user base for web browsers combined with the connectivity
of the Internet and the ease of writing web application servers
using the HTTP defined Common Gateway Interface (CGI)make web
technology very attractive for a large class of forms-based
applications.
At the same time that the Internet was growing in popularity and
acceptance, mobile computing was also increasing in popularity. The
use of laptops, notebooks, Personal Digital/Communication
Assistants (PDAs/PCAs) and other portable devices has lead to an
increase in demands for wireless communications. Wireless wide area
networks, cellular communications and packet radio, however, suffer
from common limitations if used in a web context. The high cost per
byte of communications, slow response time, low bandwidth and
unreliability all hamper use of wireless technology for the
stateless communication protocol of the World Wide Web. Also,
because the web protocol is stateless the amount of data per
request and the number of communication requests transferred over
the wireless connection are larger than would be necessary if the
communication were not self contained. Thus, combining wireless
technology, or any low-speed communication technology, with web
technology seems impractical as the strength of the web technology
in its universal nature exacerbates the weaknesses of the wireless
technology.
OBJECTS AND SUMMARY OF THE INVENTION
In view of the above limitations it is one object of the present
invention to provide a communication system which reduces the
amount of data to be transferred between applications.
It is an additional object of the present invention to provide a
communication system which may be used in a web browser/server
environment.
It is a further object of the present invention to be compatible
with existing communication protocols and languages in a low speed
or wireless communication system without requiring modification of
web browser or web server applications.
It is an additional object of the present invention to provide a
communication system which reduces the amount of communication
required between a web browser and a web server and thereby
enhances performance of the communication system.
In view of these and other objects, the present invention provides
a method of reducing the data transmitted over a communication link
from a first application resident in a first computer and to a
second application resident in a second computer where the data is
transmitted over an external communication link from the first
computer to the second computer. One aspect of the present
invention includes storing a data stream from the first application
to be provided to the second application in response to a request
from the second application in a cache resident in the first
computer to create a server base cache entry. The data stream to be
provided to the second application in response to a request from
the second application is also stored in a cache resident in the
second computer to create a client base cache entry. Requests from
the second application are evaluated to determine if a client base
cache entry corresponding to the interrogated request exists to
provide a client base form. Requests from the second application
are also interrogated to determine if a server base cache entry
corresponding to the interrogated request exists to provide a
server base form. The data stream corresponding to the response
originated by the first application in response to the interrogated
request from the second application is intercepted prior to
transmission of the response on the external communication link and
compared to the server base form to provide difference data
corresponding to the difference between the intercepted response
and the server base form. The difference data is sent to the second
computer over the external communication link and the difference
data transmitted over the external communication link sent by the
first computer is acquired from the external communication link.
The response data stream corresponding to the communication from
the first application is reconstructed from the client/server
specific data stream received over the external communication link
by combining the client base form with the difference data received
over the external communication link to create a response data
stream corresponding to the intercepted response. The reconstructed
data stream corresponding to the intercepted response is provided
to the second application.
In a further aspect of the present invention, the second computer
determines if the server base form is identical to the client base
form and the server base form and the difference data are
transmitted to the second computer over the external communication
link if the server base form is not identical to the client base
form. The intercepted response data stream corresponding to the
response from the first application is then reconstructed by
combining the server base form received over the external
communication link with the difference data received over the
external communication link to create a data stream corresponding
to the intercepted response. The client base form corresponding to
the interrogated request is also updated by storing the received
server base form as the client base cache entry corresponding to
the interrogated request.
In a server rebasing aspect of the present invention, the first
computer determines if the difference between the server base form
and the intercepted response is greater than a predefined
difference threshold. The server base form corresponding to the
interrogated request is updated by storing the intercepted response
data stream received from the first application as the server base
cache entry corresponding to the intercepted request if the
difference between the server base form and the intercepted
response is greater than the predefined difference threshold. The
comparison then utilizes the updated server base form.
In an alternative embodiment of the present invention, a plurality
of server base cache entries which correspond to the request from
the second application are maintained. A request from the second
application is interrogated to determining if a plurality of server
base cache entries exist corresponding to the request from the
second application to provide a plurality of server base forms. The
first computer determines if one of the plurality of server base
forms is identical to the client base form and utilizes the one of
the plurality of server base forms which is identical to the client
base form if one of the plurality of server base forms is identical
to the client base form.
An additional embodiment of the present invention includes updating
the server cache entry with the data stream from the first
application in response to the request from the second application.
A plurality of difference data sets which correspond to the request
from the second application and which represent the differences
between successive server cache entries are maintained to provide
archival difference data. A plurality of CRC entries are also
maintained wherein each of the plurality of CRC entries is
associated with one of the plurality of difference data sets and
uniquely identify the server base form from which the difference
data set was derived. If a plurality of difference data sets and
CRCs exist corresponding to the request from the second application
and if one of the plurality of CRCs corresponds to a server base
form which is identical to the client base form the archival
difference data corresponding to the CRC which corresponds to the
client base form, the successive archival difference data sets and
the difference data calculated for the current server base form and
the response from the first application are sent to the second
computer over the external communication link. The response data
stream corresponding to the communication from the first
application from the data stream received over the external
communication link is reconstructed by successively combining the
client base form with the difference data received over the
external communication link to create a response data stream
corresponding to the intercepted response. The client cache entry
corresponding to the request from the second application is also
updated with the reconstructed data stream.
In alternative embodiments of the present invention, the first
application comprises a web server and the second application
comprises a web browser. Alternatively, the external communication
link comprises a wireless communication link. Furthermore, an
alternative embodiment includes the request from the web browser
comprising a CGI request.
As will be appreciated by those of skill in this art, the above
described aspects of the present invention may also be provided as
an apparatus or a program product having computer-readable program
means.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a typical web browser/web server
system;
FIG. 2 is a block diagram of a web browser/web server system
according to one embodiment of the present invention utilizing a
client intercept and a server intercept;
FIG. 3 is a flow diagram depicting operations carried out by a
client-side intercept module in a preferred embodiment of the
present invention implementing a coherent caching system;
FIG. 4 is a flow diagram depicting operations carried out by a
client-side intercept module in a preferred embodiment of the
present invention implementing a coherent caching system;
FIG. 5 is a flow diagram depicting operations carried out by a
server-side intercept module in a preferred embodiment of the
present invention implementing a coherent caching system;
FIG. 6 is a flow diagram depicting operations carried out by a
server-side intercept module in a preferred embodiment of the
present invention implementing a coherent caching system;
FIG. 7 is a flow diagram depicting operations carried out by a
client-side intercept module in a preferred embodiment of the
present invention implementing a differencing data transfer
system;
FIG. 8 is a flow diagram depicting operations carried out by a
client-side intercept module in a preferred embodiment of the
present invention implementing a differencing data transfer
system;
FIG. 9 is a flow diagram depicting operations carried out by a
server-side intercept module in a preferred embodiment of the
present invention implementing a differencing data transfer
system;
FIG. 10 (which is comprised of FIG. 10A and FIG. 10B which
collectively form FIG. 10) is a flow diagram depicting operations
carried out by a server-side intercept module in a preferred
embodiment of the present invention implementing a differencing
data transfer system;
FIG. 11 is a block diagram of one aspect of the present invention
utilizing virtual sockets;
FIG. 12 is a block diagram of a client-side intercept module and a
server-side intercept module according to one embodiment of the
present invention utilizing virtual sockets;
FIG. 13 (which is comprised of FIG. 13A and FIG. 13B which
collectively form FIG. 13) is a flow diagram depicting operations
carried out by a socket manager of either the client-side intercept
module or the server-side intercept module according to one
embodiment of the present invention utilizing virtual sockets;
FIG. 14 is a flow diagram depicting operations carried out by a
client-side intercept function in one embodiment of the present
invention utilizing virtual sockets;
FIG. 15 is a flow diagram depicting operations carried out by a
server-side intercept function in one embodiment of the present
invention utilizing virtual sockets;
FIG. 16-1 is a flow diagram depicting the virtual create operation
according to one embodiment of the present invention utilizing
virtual sockets;
FIG. 16-2 is a flow diagram depicting the virtual send operation
according to one embodiment of the present invention utilizing
virtual sockets;
FIG. 16-3 is a flow diagram depicting the virtual receive operation
according to one embodiment of the present invention utilizing
virtual sockets;
FIG. 16-4 is a flow diagram depicting the virtual select operation
according to one embodiment of the present invention utilizing
virtual sockets;
FIG. 17-1 is a flow diagram depicting the virtual flush operation
according to one embodiment of the present invention utilizing
virtual sockets; and
FIG. 17-2 is a flow diagram depicting the virtual close operation
according to one embodiment of the present invention utilizing
virtual sockets.
DETAILED DESCRIPTION
The present invention now will be described more fully hereinafter
with reference to the accompanying drawings, in which preferred
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
FIGS. 3 to 10 and 13 to 17-2 are flowchart illustrations of methods
and systems according to the invention. It will be understood that
each block of the flowchart illustrations, and combinations of
blocks in the flowchart illustrations, can be implemented by
computer program instructions. These computer program instructions
may be loaded onto a computer or other programmable apparatus to
produce a machine, such that the instructions which execute on the
computer or other programmable apparatus create means for
implementing the functions specified in the flowchart block or
blocks. These computer program instructions may also be stored in a
computer-readable memory that can direct a computer or other
programmable apparatus to function in a particular manner, such
that the instructions stored in the computer-readable memory
produce an article of manufacture including instruction means which
implement the function specified in the flowchart block or blocks.
The computer program instructions may also be loaded onto a
computer or other programmable apparatus to cause a series of
operational steps to be performed on the computer or other
programmable apparatus to produce a computer implemented process
such that the instructions which execute on the computer or other
programmable apparatus provide steps for implementing the functions
specified in the flowchart block or blocks.
Accordingly, blocks of the flowchart illustrations support
combinations of means for performing the specified functions and
combinations of steps for performing the specified functions. It
will also be understood that each block of the flowchart
illustrations, and combinations of blocks in the flowchart
illustrations, can be implemented by special purpose hardware-based
computer systems which perform the specified functions or steps, or
combinations of special purpose hardware and computer
instructions.
FIG. 2 illustrates one embodiment of the present invention. As seen
in FIG. 2, a web browser 10 communicates with a client-side
intercept module 30. The web server 20 communicates with a
server-side interrupt module 40. The client-side interrupt module
30 then communicates with the server-side interrupt module 40 over
the communication link 35. The web browser 10 and the client-side
intercept module 30 may be contained in a first computer 5. The
server-side intercept module 40 and the web server 20 may be
contained in a second computer 6. The first computer 5 and the
second computer 6 communicate over external communication link
35.
Preferably, the web browser 10 is a Internet web browser utilizing
hypertext transfer protocol (HTTP) and hypertext markup language
(HTML) to communicate with an Internet web server 20 which also
uses HTTP and HTML. In operation, the web browser 10 would output
an HTTP data stream which is intercepted by the client-side
intercept module 30. The intercept of the HTTP data stream by the
client-side intercept module 30 may be accomplished through the use
of the TCP/IP loop-back feature where the client side intercept
module 30 resides at an IP address having a network number of 127,
such as 127.0.0.1. The client-side intercept module 30 then
converts or transforms the HTTP data stream into a client/server
specific protocol and transmits the client/server specific data
stream onto the external communication link 35. The server-side
intercept module 40 receives the client/server specific data stream
and reconstructs the original HTTP data stream corresponding to the
web browser originated communication. This reconstructed HTTP data
stream is then transferred to the web server 20. The web server 20
responds to the HTTP data stream in the normal manner of an
Internet web server. As will be appreciated by one of skill in the
art, the web server 20 may also be a proxy which allows multiple
browsers to connect to the Internet.
When information is received by the web server 20 for transmission
to the web browser 10, for example, in response to a browser
request for a specific URL home page, the web server 20 outputs an
HTTP data stream corresponding to the communication to be sent to
the web browser 10. This web server originated communication is
intercepted by the server-side intercept module 40 and transformed
by a client/server specific data stream. The client/server specific
data stream corresponding to the web server originated
communication is then sent on the external communication link 35
from the second computer to the first computer. The client/server
specific data stream is received by the client-side intercept
module 30 and the original HTTP data stream corresponding to the
web server originated communication is rebuilt and provided to the
web browser 10.
In a particular embodiment of the present invention, the external
communication link 35 is a wireless communication link. In such a
case, in order to obtain system performance which is acceptable to
users, it is desirable to reduce the amount of communication over
the external communication link 35 both in the frequency of the
communications and in the amount of information which must be
transferred over the communication link 35. Accordingly, the
present invention utilizes caching, differencing, and protocol
reduction techniques to minimize the amount of communication
required over the external communication link 35. These techniques
are accomplished by converting the stateless or stochastic
protocols of HTTP into a client/server specific protocol which
utilizes information specific to the client and the server to
reduce the amount and frequency of communications.
While the present invention has and will be described with respect
to a single web browser application and a single web server
application, as will be appreciated by those of skill in this art,
the benefits and advantages of the present invention may also be
achieved with multiple web browsers associated with a single web
server. Thus, the methods, apparatus and program products of the
present invention in connection with multiple browsers each
communicating with a client-side intercept module and these client
side intercept modules would then communicate with the server-side
intercept module of the web server or web proxy.
In one embodiment of the present invention, both the client-side
intercept module 30 and the server-side intercept module 40 have
cache storage capabilities. The client cache resident in the first
computer stores HTTP data streams to be received by the web browser
in response to a web browser originated communication. The server
cache resident in the second computer stores HTTP data streams
which are received from the web server in response to a browser
originated communication.
As will be appreciated by one of skill in the art, the cache
resident in the first computer or the second computer may be of any
size based upon the specific hardware configurations of the
computers. These caches store information for each communication
including, the URL of the communication, a unique identifier based
on the communications contents such as a cyclic redundancy check
(CRC) of the data of the communication, the store date time (SDT)
indicating the time when the cache entry was created or refreshed
and the data of the communication. Thus, a directory of cache
entries may be created for each communication stored in the cache.
Furthermore, because of the limited resources available in any
given hardware configuration, any number of caching techniques
known to one of skill in the art for maintaining the caches
resident in the first computer and the second computer may be
utilized. Thus, for example, the cache may invalidate the oldest
directory entry if a user defined cache size would be exceeded by
the addition of a new entry and then the new entry added in place
of the invalidated entry. Furthermore, cache entries may be
maintained over multiple instances of the web browser or web server
applications or even power-on cycles of the first or second
computers to create a persistent cache.
The operation of the caching structure according to one aspect of
the present invention will be now be described with reference to
FIGS. 3 through 6, which are flowcharts describing the operation of
the client-side intercept module 30 and the server-side intercept
module 40.
Specifically with reference to FIG. 3, block 100 indicates that the
client-side intercept module 30 has received a request from the web
browser 10. This request may take the form of an HTTP data stream.
The client-side intercept module 30 checks the uniform resource
locator (URL) of the incoming request as is reflected in block 105.
The client-side intercept module 30 determines from the URL if the
information corresponding to the web browser originated request has
previously been stored in the client cache resident in the first
computer.
If the information corresponding to the URL has not been previously
stored in the client cache, then the operations depicted in block
106 are carried out by the client-side intercept module. The
client-side intercept module 30 transmits a request on the external
communication link 35 to the server-side intercept module 40.
If, however, upon interrogating the web browser originated
communication as depicted in block 105 a client cache entry exists
which corresponds to the web browser originating communication,
then in the simplest embodiment this information would be provided
to the web browser as an HTTP data stream. However, as reflected in
FIG. 3, the preferred embodiment of the present invention performs
what is referred to herein as a coherency interval check on the
cache entry corresponding to the web browser originated
communication. This operation is reflected in block 110 of FIG.
3.
The coherency interval for a client-side intercept module may be
user defined and is the length of time which a cache entry may
exist before it becomes stale and, even if present, must be
refreshed by requesting the information corresponding to the web
browser originated communication from the web server. The coherency
interval check reflected in block 110 may be carried out by
comparing the current date and time to the sum of the SDT of the
cache entry corresponding to the web browser originated
communication and the coherency interval specified by the user. If
the current date and time is greater than this sum then the
information stored in the cache corresponding to the web browser
originated communication has become stale and the "No" branch of
block 110 is taken. However, if the current date and time is less
than the sum of the SDT plus the user defined coherency interval,
then the "Yes" branch of block 110 is taken and, as reflected in
block 111, the cache entry is supplied to the browser as an HTTP
data stream. Thus completing the browser originated communication
received by the client-side intercept module 30 in block 100 of
FIG. 3.
If the coherency interval check reflected in block 110 determines
that the cache entry resident in the first computer is stale, then
a request is made to the server-side intercept module 40 to check
the coherency of the cache entry resident in the second computer.
This operation is reflected in block 112 of FIG. 3. This is
accomplished by supplying across the external communication link 35
to the server-side intercept module 40 the coherency interval for
the particular client-side intercept module 30 the HTTP request
originated by the web browser 10 and a unique indicia of the
contents of the client cache corresponding to the URL of the web
browser originated communication. In a preferred embodiment, this
unique indicia is the results of a cyclic redundancy check or CRC
for the cache entry.
Turning now to FIG. 5 which reflects the server-side intercept
module operations in response to information received over the
external communication link 35 from the client-side intercept
module 30. When the server-side intercept module 40 receives a
request from the client-side intercept module, the server-side
intercept module 40 receives the predetermined client coherency
time interval, the CRC value for the client cache entry, and the
HTTP request originated by the web browser. The receipt of this
information is reflected in block 120 of FIG. 5.
After receiving the information from the client-side intercept
module 30, the server-side intercept module 40 checks its server
cache resident in the second computer to determine if a server
cache entry exists corresponding to the URL of the HTTP request
originated by the web browser. If, after interrogating the web
browser originated communication as reflected in block 125, the
server-side intercept module 40 determines that a cache entry does
exist corresponding to the information requested by the web browser
originated communication the "Yes" branch of block 125 is taken.
The server-side intercept module 40 then compares the current date
and time of the SSI module 40 to the sum of the SDT of the server
cache entry corresponding to the information requested by the web
browser originated communication and the predetermined client
coherency time interval received from the client-side intercept
module.
If the current date and time is less than the sum of the SDT for
the server cache entry and the coherency interval, then the "Yes"
path of block 130 of FIG. 5 is taken. The server-side intercept
module 40 then compares the CRC of the server cache entry to the
CRC of the client cache entry to determine if the two cache entries
are identical. If the two cache entries are identical, then the
"Yes" path of block 135 is taken and, as reflected in block 136, a
"coherent" response is sent to the client-side intercept module
30.
If the conditional of block 135 determines that the CRC's are not
equal, then the information contained in the client cache and the
server cache are not identical and, as reflected in block 137, the
server-side intercept module sends the server cache entry to the
first computer over the external communication link. In sending the
server cache entry to the client-side intercept module 30, the
server-side intercept module converts the entry to a client
specific communication protocol which includes the CRC of the
server cache entry, the server cache entry data, and the age of the
server cache entry. The age of the server cache entry is calculated
by subtracting from the current date and time the SDT of the cache
entry.
Finally, with respect to FIG. 5, if either the sum of the SDT plus
the predetermined client coherency time interval is less than the
current date and time or if no cache entry exists corresponding to
the URL of the web browser originated communication, then the "No"
path of block 130 or the "No" path of block 125, respectively, will
be taken. Thus, the operations of block 126 will be carried out and
the server-side intercept module 40 will send to the server the web
browser originated communication as an HTTP data stream. If the
server-side intercept module 40 must send the web browser
originated communication to the server as an HTTP data stream, then
the server-side intercept module 40 will execute the operations of
FIG. 6.
As seen in FIG. 6 block 140, in response to the web browser
originated communication, the server-side intercept module will
receive an HTTP data stream from the web server 20. Upon receipt of
the HTTP data stream, the server-side intercept module 40 will
calculate the CRC for the HTTP data stream and temporarily store
the HTTP data stream. Then, as reflected in block 145, the
server-side intercept module interrogates the HTTP data stream and
determines if a server cache entry corresponding the URL of the
HTTP data stream exists. If such an entry does exist, then the
"Yes" path of block 145 is carried out. The server-side intercept
module 40 then compares the recently calculated CRC of the HTTP
data stream received from the web server 20 with the CRC of the
server cache entry corresponding to the URL of the web server
originated response communication as reflected in block 150. If the
CRC's are the same, then the "Yes" branch of block 150 is carried
out. The server-side intercept module 40 updates the SDT entry for
the server cache entry as reflected in block 151 and empties from
temporary storage the HTTP data stream received by the web server
20 as shown in block 152.
If the results of the CRC comparisons indicate that the server
cache entry is different than the HTTP data stream received from
the web server 20, then the "No" path of block 150 is carried out.
The server-side intercept module 40 removes from the server cache
the existing data as reflected in block 153 and then, as reflected
in block 154, updates the server cache with the newer information.
As seen in block 154, this update includes storing in the server
cache the CRC of the web server communication storing as part of
the cache entry the current date and time as the SDT for the cache
entry and storing the HTTP data stream. In either case, whether a
server cache entry is updated or whether the server cache entry is
found to be identical to the HTTP data stream received from the web
server 20, the server-side intercept module then determines if the
server cache entry is identical to the client cache entry
corresponding to the web browser originating communication. This
operation is reflected in block 155.
If the server-side intercept module 40 determines that a cache
entry does not exist corresponding to the response received from
the web server 20, then the "No" path of block 145 is taken. A
server cache entry is created as reflected in block 146 by storing
the URL of the response from the web server, by storing the CRC of
the response from the web server, by storing the HTTP data stream,
and by storing as the SDT the current date and time. After creating
a cache entry corresponding to the web browser originated
communication, the server-side intercept module 40 then again
compares the CRC of this server cache entry to the CRC of the
corresponding client cache entry as reflected in block 155.
If the results of the comparison of the server cache entry to the
client cache entry indicate that the cache entries are identical,
then the "Yes" branch of block 155 is taken and the operations of
block 156 are carried out. In block 156 it is seen that the
server-side intercept module 40 sends a coherent response to the
client-side intercept module 30. The server-side intercept module
40 transforms the server request cache entry to a client/server
specific data stream by sending the coherent response and sending
an age of zero to the client-side intercept module.
If the server-side intercept module 40 determines that the client
cache entry is not identical to the server cache entry
corresponding to the web browser originated communication, then the
"No" branch of block 155 is taken and the operations of block 157
are carried out. As reflected in block 157, the server-side
intercept module 40 converts or transforms the server cache entry
into a client/server specific data stream. The data stream includes
the CRC of the server cache entry, the server cache entry HTTP data
stream, and the age of the cache entry which is set to zero. This
client/server specific communication is then transmitted over the
external communication link 35 to the client-side intercept module
30.
The functions of the client-side intercept module 30 upon receipt
of a communication from the server-side intercept module will now
be described with respect to FIG. 4. As seen in block 160, the
client-side intercept module 30 receives or acquires the
client/server specific data stream which was transmitted over the
external communication link 35. The client-side intercept module
then determines what type of response was received from the
server-side intercept module 40 as reflected in block 165. If the
server-side intercept module 40 indicates that the client cache
entry is coherent, i.e. the server cache entry and the client cache
entry are identical, then the operations reflected in block 166 are
carried out. As seen in block 166, the client-side intercept module
30 updates the SDT of the client cache entry corresponding to the
web browser originated communication with the difference between
the current date and time and the age received from the server-side
intercept module 40. Thus, without synchronizing the two clocks of
the first computer 5 and the second computer 6, the present
invention has revised the coherency time of the cache entry of the
first computer to reflect the newer data of the second computer.
After updating the SDT for the client cache entry corresponding to
the web browser originated communication, the client-side intercept
module 30 transfers the client cache entry to the web browser 10 as
an HTTP data stream. This operation is shown in block 174.
If, however, the client-side intercept module 30 determines that
the response type is a data or data stream response, then the
"stream" path out of block 165 is taken and the operations of block
167 are carried out. The client-side intercept module 30 receives
the HTTP data stream and temporarily stores this data. Then, as
reflected in block 170 of FIG. 4, the client-side intercept module
30 determines if a cache entry exists corresponding to the web
browser originated communication. If a cache entry exists, then the
"Yes" path of block 170 is taken and, as reflected in block 171,
the existing cache entry is flushed. The client-side intercept
module then updates the client cache entry corresponding to the web
browser originated communication by storing the CRC of the HTTP
data stream received from the server-side intercept module 40, by
storing as the SDT the difference between the current date and time
and the age received from the server-side intercept module 40, and
by storing the HTTP data stream. This operation is reflected in
block 172.
If no cache entry exists corresponding to the web browser
originated communication, then the "No" path of block 170 is taken.
A client cache entry is created by carrying out the operations
reflected in block 173. As seen in block 173, the client-side
intercept module 30 creates a client cache entry by storing the URL
of the HTTP data stream received from the server-side intercept
module 40 by storing the CRC of the HTTP data stream received from
the server-side intercept module 40 and by storing the HTTP data
stream. The client-side intercept module 30 also updates the SDT or
stores the SDT by subtracting from the current date and time the
age received over the external communication link 35 from the
server-side intercept module 40.
However, a client cache entry is created whether through the
operations of blocks 166, 172, or 173, the client-side intercept
module transfers or provides the client cache entry to the web
browser 10 as an HTTP data stream. These operations are reflected
in block 174 of FIG. 4.
As will be appreciated by one of skill in the art, the client cache
and the server cache may be implemented with memory or with mass
storage such as hard disks, read/write CD-ROMS, optical disks, or
other storage technologies. Furthermore, as will be appreciated by
one of skill in the art, the client-side intercept module and the
server-side intercept module may be implemented through software,
hardware, or a combination thereof.
While references made to caches being resident in a particular
first or second computer, as will be appreciated by one of skill in
the art, the benefits of the present invention may be achieved even
though the cache is not resident in the first computer but is
simply on the same side of the external communication link as the
computer. Thus, a hardware cache could be implemented external to
the first computer that serves as a client cache and connected to
the first computer by high speed communications and yet, as long as
the cache is on the same side of the external communication link as
the first computer, the benefits of the present invention will be
achieved.
In an alternative embodiment of the present invention, the
server-side intercept module 40 does not maintain a copy of the
HTTP data stream received from the web server 20 but simply
maintains a directory entry for the communication. The directory
entry would include the URL of the communication, the CRC
calculated for the HTTP data stream and the time when the HTTP data
stream was received from the web server and the SDT for the
communication which may be set to the time when the CRC was
calculated. In such a case when the client-side intercept module 30
sends a request to the server-side intercept module 40 for a
communication which corresponds to a URL for which the server-side
intercept module has maintained a CRC and SDT, then the server-side
intercept module checks the CRC received from the client-side
intercept module 30 to determine if it corresponds to the CRC of
the latest HTTP data stream for the specified URL. If there is a
match, then a coherent response is sent to the client-side
intercept module. If there is not a match, then the server-side
intercept module sends the HTTP data stream received from the
client-side intercept module to the web server 20 and returns to
the client-side intercept module 30 the response received from the
web server 20.
FIG. 7, 8, 9, and 10 reflect the operations carried out by the
client-side intercept module 30 and the server-side intercept
module 40 in another aspect of the present invention which utilizes
differencing to reduce the data transferred over the external
communication link 35. As seen in FIG. 7, block 200 illustrates the
receipt by the client-side intercept module 30 of an HTTP request
from the web browser 10. As reflected in block 205, the client-side
intercept module 30 interrogates the intercepted HTTP request from
the web browser 10 to determine if the request is to a common
gateway interface (CGI). If the request is not to a common gateway
interface, then the client-side intercept module 30 passes the
request to the server-side intercept module as reflected in FIGS. 3
through 6 and is illustrated by block 206 of FIG. 7.
If, however, the web browser originated communication corresponds
to a CGI request, then the "Yes" path out of block 205 is taken. As
reflected in block 210, the client/server intercept module 30
determines if a client base cache entry exists corresponding to the
HTTP data stream which was previously to be provided to the web
browser in response to a corresponding CGI request. This
interrogation of the CGI request may be accomplished by comparing
the URL of the web browser originated communication to the URLs
stored in the client base cache.
The client base cache may be initialized by storing the first HTTP
data stream received by the client-side intercept module 30 which
is to be provided to the web browser 10 for a given URL. This base
cache entry may be maintained over numerous instances or sessions
of the web browser 10. The client base cache entries may be updated
as reflected in FIGS. 7, 8, 9, and 10. If a client base cache entry
exists corresponding to the URL for the web browser originated
communication, then the CRC to be sent to the server-side intercept
module 40 over the external communication link 35 is set equal to
the CRC for the client base cache entry as reflected in block 211
of FIG. 7. If no client base cache entry exists, then the "No" path
out of block 210 of FIG. 7 is taken and the CRC for the request to
be sent over the external communication link 35 to the server-side
intercept module 40 is nulled. This operation is reflected in block
212 of FIG. 7.
Block 213 illustrates the operations of sending the CGI request to
the server-side intercept module 40 over the external communication
link. As reflected in block 213, the client-side intercept module
30 transmits the HTTP request and the request CRC which has either
been set to null if no client base cache entry exists for the URL
of the CGI request or has been set to the CRC of the client base
cache entry if an entry does exist. Thus, the client-side intercept
module has converted the CGI request to a client/server specific
protocol, transmitted the client/server specific communication over
the external communication link to be received by the server-side
intercept module 40.
The actions taken by the server-side intercept module when a CGI
request is received are reflected in FIG. 9. The receipt of the CGI
request by the server-side intercept module 40 is shown in block
220. When the server-side intercept module 40 receives the CGI
request, it saves a copy of the CRC value and the HTTP request. As
seen in block 221, the server-side intercept module 40 passes the
HTTP request to the web server 20.
When the server-side intercept module 40 receives a response to the
HTTP request corresponding to the web browser originated
communication or CGI request, the server-side intercept module 40
receives this response as an HTTP data stream as reflected in block
230 of FIG. 10. As seen in block 230, the server-side intercept
module 40 saves the HTTP data stream and computes a CRC value for
the HTTP data stream received from the web server 20. The
server-side intercept module 40 also nulls the difference value to
initialize the difference data. The server-side intercept module
then determines if the response received as a web server originated
communication is a response to a CGI request as shown in block 235.
If the answer is no, then the "No" path out of block 235 of FIG. 10
is taken and the operations of block 236 are executed to send the
HTTP data stream to the client-side intercept module. As reflected
in block 236, this operation may involve the caching operations
described in FIGS. 3 through 6. If the response received in block
230 is a response to a CGI request, then the "Yes" path out of
block 235 is taken and the server-side intercept module then
determines if a server base cache entry exists for the CGI response
as reflected in block 240.
A server base cache entry may be created the first time the
server-side intercept module 40 receives a response to a CGI
request. In this instance the result of the conditional reflected
in block 240 will cause the "No" path to be taken out of block 240.
The server-side intercept module 40 will then create a server base
cache entry corresponding to the CGI request by storing the URL for
the CGI, the HTTP data stream for the response to the CGI request,
and the CRC for the HTTP data stream. This operation is reflected
in block 241. To be compatible with the coherent cache system
described in FIGS. 3 through 6, the server base cache entry may
also include the SDT. As used herein, the term server CGI base form
refers to the server base cache entry corresponding to the CGI
request received from the web browser 10.
If a server base cache entry exists corresponding to the CGI
request then the "Yes" path out of block 240 is taken. The
server-side intercept module compares the CRC of the server base
cache entry to the CRC of the response received from the web server
20. These operations are reflected in block 245 of FIG. 10. If the
CRCs are the same, then the server-side intercept module determines
if the CRC for the server base cache entry corresponds to the CRC
for the client base cache entry. If these two CRC values are the
same, then the client base cache entry, the server base cache
entry, and the response received from the web server 20 all contain
the same HTTP data stream. The comparison of the server base cache
entry to the client base cache entry is reflected in block 250.
If the two base cache entries are the same, then the server-side
intercept module need not send the base cache entry to the
client-side intercept module 30 and so, as reflected in block 251,
the HTTP data stream data to be transferred to the client-side
intercept module 30 is nulled. The server-side intercept module 40
then converts the HTTP data stream received from the web server 20
to a client/server specific communication protocol by transmitting
the CRC of the HTTP data stream stored in the server base cache
corresponding to the CGI request, the nulled HTTP data stream data
and the nulled difference data to indicate that the response to the
CGI request was identical to the client base cache entry, as
illustrated in block 252.
Returning to block 245, if the CRC for the server base cache entry
corresponding to the CGI request is different than the CRC for the
response received from the web server in response to the CGI
request originated by the web browser, then the "No" path out of
block 245 is taken. The server-side intercept module 40 then
carries out the operations reflected in block 246. The server-side
intercept module 40 compares the intercepted CGI response to the
server base cache entry corresponding to the intercepted CGI
request or the server CGI base form. This comparison of the
intercepted CGI response to the server CGI base form provides CGI
difference data which corresponds to the difference between the
intercepted CGI response and the server CGI base form.
The differencing may be performed by any method known to those of
skill in the art for determining the difference between a base form
and a modified form. One method of differencing suitable for use in
the present invention is described in "a Cross-Platform Binary
Diff" by Coppieters, Dr. Dobb's Journal, May 1995, pp. 32-36, the
disclosure of which is incorporated herein by reference as if set
forth fully. Other methods which may be used in determining the
difference data include those described in IBM Technical Disclosure
Bulletin, Vol. 22, No. 8A, January 1980 which is also incorporated
herein by reference as if set forth fully.
The server-side intercept module 40 then determines if the server
CGI base form requires updating as reflected in block 247. This
determination may be made by determining if the average difference
data between the intercepted CGI response and the server CGI base
form is over a predefined threshold. Other methods of determining
if the server base cache entry corresponding to the CGI request
should be updated may include time coherency such as that described
in FIGS. 3 through 6 or other methods known to those with skill in
the art to determine if the difference data has increased to such
an extent that rebasing to create a new base cache entry would
improve system performance.
If rebasing of the server is not required, then the "No" path out
of block 247 is taken and the server-side intercept module 40
carries out the operations of block 250 to determine if the CRC of
the client base cache entry is the same as that of the server base
cache entry or the server CGI base form is identical to a client
CGI base form which are the base cache entries of the server and
the client which correspond to the particular CGI request of the
web browser originated communication. If the base forms are the
same, then the client does not need to be rebased and the HTTP data
stream information is nulled, as reflected in block 251. The
server-side intercept module 40 then sends the difference response
to the client-side intercept module 30 by sending the CRC of the
server base cache entry corresponding to the CGI request (i.e. the
CRC of the server CGI base form), by sending the nulled HTTP data
stream which would correspond to the base data and by sending the
difference data determined in block 246. These operations are again
reflected as block 252 of FIG. 10.
If the server-side intercept module 40 determines that the CRCs are
not the same for the client CGI base form and the server CGI base
form, then the client needs to be rebased. The client rebasing
operation consists of sending the server CGI base form to the
client-side intercept module 30. To perform this operation, the
server-side intercept module sets the HTTP data stream data to be
sent to the client-side intercept module 30 equal to the server CGI
base form. This operation is reflected in block 253. The
server-side intercept module 40 then converts the HTTP data stream
received from the web server to a client/server specific protocol
by sending the CRC of the server CGI base form, the HTTP data
stream data corresponding to the server CGI base form, and sending
the difference data between the CGI base form and the response
received from the web server as seen in block 252. This information
is then transmitted over the external communication link 35 to the
client-side intercept module 30.
Returning to block 247, if server rebasing is required then the
"yes" path out of block 247 is taken. As reflected in block 248 the
server side intercept module updates the server base cache entry
corresponding to the browser originated communication with the HTTP
data stream received from the web server. The CRC of the response
is also updated and the CGI difference data is nulled. The server
side intercept module then compares the CRC of the new server side
cache entry as reflected in block 250 and completes the transfer as
described above.
The operations of the client-side intercept module upon receipt of
a response from the server-side intercept module 40 are shown in
FIG. 8. The receipt of the response from the server-side intercept
module 40 by the client-side intercept module 30 is reflected in
block 260. As seen in block 265, the client-side intercept module
30 determines if the response is a response to a CGI request. If
the response is not to a CGI request, then the client-side
intercept module carries out the operations of block 267 which may
include the cache operations reflected in FIGS. 3 through 6. If,
however, the response is to a CGI request, then the "Yes" path out
of block 265 is taken. The client-side intercept module 30 saves
the HTTP data stream data, the difference data, and the CRC
acquired from the client/server specific data stream transmitted
over the external communication link. These operations are
reflected in block 266 of FIG. 8.
The client-side intercept module 30 then determines if a client
base cache entry corresponding to the intercepted CGI request
exists which would contain a client CGI base form. This
interrogation is shown in block 270 and may be carried out by
examining the URL of the HTTP request or HTTP response. If a client
CGI base form exists, then the "Yes" path out of block 270 is
taken. The client-side intercept module 30 then compares the CRC
received over the external communication link to that of the CRC of
the client CGI base form as shown in block 275. If they are
different, then the "No" path of block 275 is taken and the client
rebases by updating the CGI base form by replacing the client base
cache entry corresponding to the URL of the CGI request of the web
browser originated communication with the HTTP data stream data
received over the external communication link 35 from the server
side intercept module 40. The client base cache entry also is
updated with respect to the CRC for the HTTP data stream. These
operations are reflected in block 276 of FIG. 8.
If the CRC received over the external communication link 35 is the
same as the CRC of the CGI base form, then the server-side
intercept module server CGI base form is the same as the
client-side intercept module client CGI base form and the "Yes"
path out of block 275 is taken.
Whether the base forms are the same or the client is rebased, the
operations reflected in block 277 are carried out by the
client-side intercept module 30. Block 277 reflects the client-side
intercept module 30 reconstructing the HTTP data stream
corresponding to the communication from the web server 20 from the
client/server specific data stream received over the external
communication link 35 by combining the client CGI base form with
the CGI difference data received over the external communication
link 35 to create an HTTP data stream corresponding to the
intercepted CGI response. As seen in block 278, this response is
then provided to the web browser 10 as an HTTP data stream.
If no CGI base form exists in the client corresponding to the URL
of the CGI request, then the "No" path out of block 270 of FIG. 8
is taken. As seen in block 271, the client-side intercept module 30
creates a client base cache entry corresponding to the URL of the
CGI request by storing the URL, the CRC of the HTTP data stream
received over the external communication link from the server-side
intercept module 40, and the actual HTTP data stream data. Storing
this information creates a client base cache entry corresponding to
the intercepted CGI request and thus creates a client CGI base
form. The client-side intercept module may then carry out the
operations of block 277 by reconstructing the HTTP data stream by
combining or merging the client CGI base form with the CGI
difference data which may have been nulled.
The present differencing techniques may also be applied to non-CGI
data. In such an instance, the server-side intercept module 40
would need to keep multiple generations of server base cache
entries to allow for the possibility that client-side intercept
modules of web browsers connected to the web server may have
different base forms. The server-side intercept module could then
compare the CRC received from the client-side intercept module with
the CRC of each of the prior generations of server base forms until
a match was obtained. The server-side intercept module 40 may then
optionally rebase the client-side intercept module 30 or simply
provide the difference data to the client-side intercept module 30.
Thus, the differencing methodologies described herein with respect
to the CGI request may apply equally to any HTTP request and
response.
While the above system of maintaining multiple generations of base
forms may allow for the use of differencing with non-CGI requests,
this methodology is more memory or storage intense and does not
fully exploit the caching capabilities described above. To reduce
memory or storage requirements and exploit the caching methods
described above, the following preferred method of using
differencing for non-CGI requests may be utilized. In this
preferred implementation the server side intercept module
calculates the difference between the a server base form
corresponding to the request and the HTTP data stream of the
response from the web server. This difference data is then stored
by the server side intercept module. The server base form is then
updated by replacing the base form with the new response from the
web server, including updating the CRC of the base form. However,
rather than discarding the old CRC, the CRC's for previous base
forms are stored as is the difference data. The prior generations
of difference data and CRCs are then selectively transmitted to the
client side intercept module based upon the CRC of the client base
form corresponding to the non-CGI request.
As an example of the non-CGI differencing method, if the server
side intercept module receives a non-CGI request this request would
also be accompanied by the CRC of the base form resident in the
client side intercept module corresponding to the URL of the
non-CGI request. When the server side intercept module received the
response from the web server it would calculate the CRC of the
response. The server side intercept module would then calculate the
difference between the response and the server base form for the
URL and save this difference data. The server side intercept module
would update the server base form with the response data and
archive the CRC of the previous base form and the difference data
between the response and the old base form. The server side
intercept module would then compare the CRC of the client base form
with the server base form CRC and any stored or archived CRCs to
determine if a match is found. If no match is found the response is
simply sent to the client side intercept module.
If a match is found then the difference data corresponding to the
CRC match and any subsequent difference data up to and including
the current difference data is sent to the client side intercept
module. The client side intercept module then applies the
difference data to the client base form to reconstruct the
response. Thus, if the CRC match occurred with a CRC for a base
form which was three generations old then three sets of difference
data would be sent to the client side intercept module and the
construction of the response would be accomplished by applying
three successive difference data sets to the client base form. If
however, the number of difference data sets or the sizes of the
difference data sets required to reconstruct the response is so
great that sending the actual response would require less data
transfer then the response itself may be sent by the server side
intercept module. In any event, after reconstructing or receiving
the response the client side intercept module would update the
client base form for the URL of the request with the response data
and update the CRC with the CRC for the response. Because the
client base form is updated each time a response is received for a
particular URL, the client cache described above may be utilized as
the cache for the client base form, thereby eliminating the need
for a separate cache of the client base forms if differencing is
utilized on non-CGI requests.
In a further aspect of the present invention, additional
communication savings may be achieved based upon the redundancy of
a stateless communication protocol such as HTTP. In such a
protocol, the client transmits information about itself to the
server each time a communication is initiated. Likewise, the server
communicates specific information about itself to the client each
time a response is initiated.
In one alternative embodiment of the present invention, the first
computer 5 communicates to the second computer 6 the computer
specific information corresponding to the predefined
characteristics of the first computer. The second computer stores
this computer specific information. The first computer then removes
the computer specific information from subsequent web browser
originated communications prior to transmission on the external
communication link 35. The second computer 6 then rebuilds the
original web browser originated communication by combining the
stored computer specific information with the subsequent
communication received over the external communication link 35 to
create an HTTP data stream.
In addition to removing the computer specific information from
communications originated by the web browser, this computer
specific information may also be removed from communications
originated by the web server. In such a case, the second computer 6
of FIG. 2 provides to the first computer 5 over the external
communication link 35 the computer specific information
corresponding to the predefined characteristics of the second
computer 6. The first computer 5 stores the computer specific
information to provide server header information. On subsequent
communications, the second computer 6 removes the computer specific
information from the web server originated communication and
transmits the remaining portion of the web server originated
communication on the external communication link 35. The first
computer 5 receives the communication over the external
communication link and rebuilds the original web server originated
communication by combining the server header information with the
client/server specific data stream received over the external
communication link to create an HTTP data stream. In both
instances, the operations of removing the computer specific
information and storing the information to create either server
header information or client header information are carried out by
the client-side intercept module 30 or the server-side intercept
module 40, depending upon whether the operation takes place in the
first computer 5 or the second computer 6.
In one embodiment of the present invention, the web browser 10
communicates to the client-side intercept module 30 using the
Transmission Control Protocol/Internet Protocol (TCP/IP). TCP may
also be used for a communication between the client-side intercept
module 30 and the server-side intercept module 40 over the external
communication link 35. Finally, TCP may be used for communication
between the server-side intercept module 40 and the web server 20.
While TCP may be used for communications between the various
components that make up the system of the present invention, the
HTTP protocol does not provide the most efficient means for
communication over an external communication link. To increase the
performance of the external communication link 35, one embodiment
of the present invention creates what are referred to herein as
"virtual sockets" which are utilized in the connection between the
web browser and the client-side intercept module 30 and between the
server-side intercept module 40 and the web server 20. The
operation of these virtual sockets will now be described with
reference to FIGS. 11 through 17.
FIG. 11 is a block diagram of one possible implementation of the
present invention utilizing the concept of virtual sockets. As seen
in FIG. 11, the first computer 5 and the second computer 6 are
connected over the external communication link 35. The web browser
10 has a plurality of real sockets which connect the web browser 10
to the client-side intercept module 30. As seen in FIG. 11, the
first real socket is depicted as 65a on the web browser 10 and the
corresponding socket is 65b on the client-side intercept module 30.
This first real socket is the TCP socket over which the web browser
10 requests further connections from the client-side intercept
module 30.
When the web browser 10 requests a new TCP connection, a
communication occurs over the real socket 65a which is received at
the real socket 65b. The client-side intercept module 30 will then
create another real socket for communication with the web browser
10. As seen in FIG. 11, a plurality of real sockets are created on
the web browser 10 with a corresponding real socket being created
on the client-side intercept module 30. These real sockets are
depicted as 60a through 64a on the web browser 10 and 60b through
64b on the client-side intercept module 30. These real sockets are
the means through which the web browser 10 communicates with the
client-side intercept module 30. After creating the real sockets
60a through 64a and 60b through 64b, communications over these
sockets are multiplexed onto a real socket 36a which provides
access for the client-side intercept module 30 to the external
communication link 35. Real sockets 36a and 36b are created when a
request is sent over real socket 37a of computer 5 to real socket
37b of computer 6. Upon receipt of the connection request by real
socket 37b, real sockets 36a and 36b are created. Sockets 37a and
37b act as the first real sockets for communication between the
client side intercept module and the server side intercept module
and may only be utilized for establishing the connection between
the two modules reflected by sockets 36a and 36b. Each of these
real sockets operates under standard TCP/IP protocols. When
communications are received by the second computer 6 over the
external communication link 35, they are received at real socket
36b. The server-side intercept module 40 then demultiplexes the
communications received at socket 36b and provides them to the
appropriate socket for transmission to the web server 20. Thus, for
example, a communication over socket 60a to socket 60b for a
request of information from a specific URL would be multiplexed
onto socket 36a, received by socket 36b, demultiplexed by the
server-side intercept module 40, and transmitted from socket 60c to
socket 60d on the web server 20. Likewise, communications occurring
over socket 61a are received by socket 61b, multiplexed by the
client-side intercept module 30, and transmitted from socket 36a to
socket 36b where the server-side intercept module 40 demultiplexes
the communication and transmits it over socket 61c to socket 61d.
Thus, communications over socket 60a and 60b, 61a and 61b, 62a and
62b, 63a and 63b, and 64a and 64b are transmitted over the
respective corresponding sockets between the server-side intercept
module 40 and the web server 20 of socket 60c and socket 60d,
socket 61c and 61d, socket 62c and socket 62d, socket 63c and
socket 63d, and socket 64c and 64d.
In a similar manner, responses to requests from web browser 10 by
the web server 20 are also transmitted over sockets connecting the
web server 20 to the server-side intercept module 40 and over the
external communication link 35 to the client-side intercept module
30, and then to the web browser 10. Thus, for example, a response
originated by web server 20 could be sent over socket 60d to socket
60c and multiplexed by the server-side intercept module 40 onto
socket 36b where it is transmitted over the external communication
link 35 to socket 36a. The client-side intercept module 30 then
demultiplexes the communication and provides it to socket 60b for
transmission to socket 60a on the web browser 10. A similar
communication path is established for each socket being utilized by
the web browser 10 or the web server 20. As will be appreciated by
one of skill in the art, while the present invention has been
described with respect to 4 socket connections between the web
browser 10 and the web server 20, any number of sockets may be
opened for providing communication access between the web browser
10 and the web server 20.
FIG. 12 is a block diagram illustrating the implementation of the
virtual socket system in the client-side intercept module 30 and
the server-side intercept module 40. External to these modules the
real sockets between the client-side intercept module 30 and the
web browser 10 and the server-side intercept module 40 and the web
server 20 function as normal TCP/IP sockets. Thus, the use of
virtual sockets is transparent to the web browser 10 and the web
server 20.
A particular embodiment of the present invention will be described
with respect to the block diagram FIG. 12 and the flow diagrams of
FIGS. 13 through 17. FIG. 13 is a flow chart for the socket manager
depicted as block 68 in FIG. 12. Referring to FIG. 13, block 300
reflects the creation of the real socket manager 68 of the
client-side intercept module 30. After the real socket manager 68
is created, it creates a first real socket shown as socket 65b in
FIG. 12. The creation of this first real socket is reflected as
block 301 of FIG. 13. After creating the first real socket 65b, the
socket manager 68, resident in the client-side intercept module 30,
also referred to herein as the client socket manager, waits for an
event on the first real socket 65b as is seen in block 302 of FIG.
13. When an event is received on the first real socket 65b, the
real socket manager 68 examines the event and, based upon that
examination, takes one of five paths as reflected in block 305 of
FIG. 13.
If a real socket is created in response to a communication request
received at the first real socket 65b, then, as reflected in the
path from block 305 to block 306 of FIG. 13, the real socket
manager 68 adds the real socket to the real event list. The real
socket manager then creates a simplex virtual socket as indicated
in block 307. In the case of the client-side intercept module, the
real socket manager initiates an application function which carries
out functions of the client-side intercept module for the virtual
socket created as reflected in block 308 of FIG. 13.
As used herein, the term "simplex socket" or "simplex virtual
socket" refers to a socket which connects directly to either a
single socket or a single application. As used herein, "multiplex
socket" refers to a socket which connects to a plurality of other
sockets. Thus, the multiplex socket carries out a multiplexing or
demultiplexing function and the simplex socket preforms a
one-to-one connection. Thus, for example, in carrying out the
functions of blocks 306 through 308 of FIG. 13, the client socket
manager 68 would, in response to the first connection request
received by the first real socket 65b, create real socket 60b,
simplex virtual socket 70, and initiate the client-side intercept
function in an application 80. Similarly for subsequent events
where a real socket is created, the real socket manager would
create real sockets 61b, 62b, 63b, or 64b and simplex virtual
sockets 71, 72, 73, or 74, and initiate a CSI function
corresponding to the created real and virtual sockets depicted as
blocks 81, 82, 83, or 84 of FIG. 12.
The operation of the client-side intercept function will now be
described with reference to the real socket 60b, the simplex
virtual socket 70, and the client-side intercept function 80
reflected in FIG. 12. Block 325 of FIG. 14 reflects the creation of
the client-side intercept function 80. Upon creation, the
client-side intercept function 80 waits for an event on the simplex
virtual socket 70 as indicated in block 326. This wait operation is
carried out by performing the virtual select function which is
described in FIG. 16-4. Upon receipt of an event, the event is
examined as reflected in block 330. If the event is a virtual
socket close, then the client-side intercept function 80 deletes
the simplex virtual socket 70 as reflected in block 349 and
terminates as reflected in block 350 of FIG. 14.
If the event is the receipt of data, then the path from block 330
to block 331 is taken and the client-side intercept function 80
receives the browser originated communication from the simplex
virtual socket 70 by executing the virtual receive operation
described herein with reference to FIG. 16-3. The client-side
intercept function then carries out the function of the client-side
intercept module as described above (see for example FIGS. 3 and
7), which is reflected in block 332. The client-side intercept
function 80 then creates a multiplex virtual socket 90 which is
connected to the real socket 36a in the client-side intercept
module 30. Real socket 36a is connected to real socket 36b on the
server-side intercept module 40. The creation of the multiplex
virtual socket is reflected in block 333 of FIG. 14 and carried out
by performing the virtual create operation described herein with
reference to FIG. 16-1. Block 334 reflects the operation of sending
the information received from the web browser over the real socket
60b and the simplex virtual socket 70 after the client-side
intercept function 80 is carried out for the web browser originated
communication. This communication is queued to the multiplex
virtual socket 90 by performing the virtual send operation
described herein with reference to FIG. 16-2. The client-side
intercept function 80, after queuing the request to the multiplex
virtual socket 90, flushes the data queued in the multiplex virtual
socket 90 as reflected in block 335 of FIG. 14, and then waits for
an event on the multiplex virtual socket as reflected in block 336.
The virtual flush function is carried out by performing the virtual
flush operation described herein with reference to FIG. 17-1 which
takes the data from the multiplexed virtual socket queue and
provides the data to the real socket 36a. The wait operation may be
carried out by performing the virtual select function described in
FIG. 16-4. At this point, the client-side intercept module has
intercepted the web browser originated communication and
transferred the communication to the server-side intercept module
over the external communication link 35.
Returning to FIG. 13, which reflects the flowchart for the socket
manager in either the server-side intercept module 40 or the
client-side intercept module 30. The real socket manager in the
server-side intercept module or the server socket manager, shown as
block 69 in FIG. 12, carries out the same function as the client
socket manager shown as block 68. In creating a first real socket
as shown in block 301, the server-side intercept module 30 creates
a "well known port" 37b for receiving requests for sockets from the
client-side intercept module 30 associated with the server-side
intercept module 40. When a real event occurs on the real socket
36b of the server-side intercept module 40, the event is examined
as reflected in block 305. In the present case, the event is the
receipt of data from real socket 36a and so the path from block 305
to block 320 of FIG. 13 is taken. The data received on real socket
36b is examined and, in our present example, because the data is a
web browser originated communication transmitted by the client-side
intercept module, a new virtual socket must be created in the
server-side intercept module 40. Thus the path from block 320 to
block 321 of FIG. 13 is taken. The server socket manager 69 then
carries out the operations reflected in block 321, block 322, block
323, and block 324 of FIG. 13. The server socket manager 69 creates
a multiplex virtual socket 95, as shown in block 321, cancels the
multiplex socket activity timer as reflected in block 322 and
initiates an application of the server-side intercept function as
reflected in block 323 of FIG. 13 and shown as block 85 in FIG. 12.
The data received at the real socket 36b is then queued to the
multiplex virtual socket 95 and a virtual event is signaled.
The creation of the server-side intercept function, as reflected in
block 323, is shown as block 360 of FIG. 15. After creation of the
server-side intercept function 85, the function receives the data
from the multiplex virtual socket 95 which was sent from the
client-side intercept module 30 and corresponds to the web browser
originated communication. This operation is reflected as block 361
of FIG. 15. After receiving the data from the client-side intercept
module, the server-side intercept function 85 processes the data as
described above for the server-side intercept module. The carrying
out of the server-side functions is reflected in block 362 (see for
example FIGS. 5 and 9). After processing the information, the
server-side intercept function 85 creates a simplex virtual socket
75 by performing a virtual create, the operation of which is
described herein with reference to FIG. 16-1. This operation is
reflected in block 363 of FIG. 15. The server-side intercept
function 85 then sends the web browser originated communication to
the simplex virtual socket 75 as shown in block 364 by performing a
virtual send, the operation of which is describe herein with
reference to FIG. 16-2. The server-side intercept function 85 then
performs a virtual flush to flush data queued in the simplex
virtual socket 75 to the real socket 60c and waits for an event on
the simplex virtual socket 75. The virtual flush operation is
described herein with reference to FIG. 17-1. The send and flush
operations are shown in blocks 364 and 365 of FIG. 15. The wait
operation may be carried out by performing the virtual select
function described in FIG. 16-4. When the server-side intercept
function 85 created the simplex virtual socket 75, a corresponding
real socket 60c was also created. By sending the web browser
originated communication to the simplex virtual socket 75, the
server-side intercept function 85 transferred the web browser
originated communication to the web server.
When the server-side intercept module 40 receives the response from
the web server on the real socket 60c, a real event occurs and the
server socket manager 69 exits block 302 of FIG. 13 and examines
the event which occurred on real socket 60c as reflected in block
305. In the present case, it will be data for an existing virtual
socket and the path from block 320 of FIG. 13 to block 324 will be
taken. The data received on the real socket 60c is queued to the
virtual socket 75 and a virtual event is signaled. When the virtual
event is signaled, the virtual-side intercept function 85 exits
block 366 of FIG. 15 and examines the event as shown in block 370.
If the event is a socket closed, then an error condition occurs and
an error message is constructed as the response as shown in block
375 of FIG. 15. However, if the event is the receipt of data, then
the path from block 370 to block 371 is taken and the server-side
intercept function 85 performs a virtual receive, as described
herein with reference to FIG. 16-3, to obtain the server response
from the simplex virtual socket 75 as shown in block 371. The
server-side intercept function 85 then performs a virtual close of
the simplex virtual socket 75 as reflected in block 372 and
described herein with reference to FIG. 17-2 and processes the
response as described above for the server-side intercept module
and shown in block 373 (see for example FIGS. 6 and 10).
Whether the exit path of block 370 of FIG. 15 is the error path to
block 375 or the data path to block 371, at block 374 the simplex
virtual socket 75 is deleted. The server-side intercept function
then performs a virtual send operation to the multiplex virtual
socket 95 to transmit the web server originated communication to
the client-side intercept module 30, as shown in block 376. The
server-side intercept function 85 then performs a virtual flush
operation to flush the data queued in the multiplex virtual socket
95. These operations are shown in block 377. The server-side
intercept function 85 then performs a virtual close operation to
close the multiplex virtual socket 95 as shown in block 378 of FIG.
15. Finally, the server-side intercept function 85 deletes the
multiplex virtual socket and terminates, as reflected in blocks 379
and 380.
The server-side intercept function performs the virtual send and
flush operations to the multiplex virtual socket 95. These trigger
events on the real socket 36a and the client socket manager 68
exits block 302 and examines the event, as shown in block 305,
because the data is received on real socket 36a, the path from
block 305 to block 320 of FIG. 13 is taken and the data is queued
to multiplex virtual socket 90. Therefore, when real sock 36a
receives the web server response from real socket 36b over the
external communication link 35, this information is demultiplexed
and provided to the appropriate multiplex virtual socket. The
receipt of the data causes a virtual event to occur as shown in
block 324 of FIG. 13 and block 336 of FIG. 14 would be exited and
the client-side intercept function 80 would examine the event as
reflected in block 340 of FIG. 14.
If the event is a socket closed response, then the path from block
340 to block 345 of FIG. 14 is taken and the client-side intercept
function 80 creates an error message response and proceeds to block
344 of FIG. 14. If the event is data received, as would be the case
in the present example, then the path from block 340 to block 341
of FIG. 14 is taken and the client-side intercept function 80
performs a virtual receive operation to receive the response from
the multiplex virtual socket 90. This receive operation is
reflected in block 341 of FIG. 14. After receiving the data from
the multiplex virtual socket 90, the client-side intercept function
80 performs a virtual close operation to close the multiplex
virtual socket 90 as reflected in block 342. The client-side
intercept function 80 then processes the response as described
above for the client-side intercept module as reflected in block
343 (see for example FIGS. 4 and 8).
The operations of block 344 are then carried out whichever path is
taken exiting block 340. The client-side intercept function 80
deletes the multiplex virtual socket as shown in block 344 and then
performs the virtual send operation to send the response to the
browser via the simplex virtual socket 70 as shown in block 346.
When the virtual send operation completes, the client-side
intercept function 80 performs a virtual flush operation to flush
the data queued in the simplex virtual socket as shown in block 347
to the real socket 60b and then performs a virtual close operation
to close the simplex virtual socket as shown in block 348. After
closing the simplex virtual socket to the client-side intercept
function the simplex virtual socket is deleted and the client-side
intercept function terminates as shown in blocks 349 and 350 of
FIG. 14.
As will be appreciated by one of skill in the art, the present
invention has been described with respect to one particular
instance of the creation of simplex and multiplex virtual sockets
and client-side intercept and server-side intercept functions,
however, a plurality of these functions may be created within a
single client-side intercept module or server-side intercept
module. Accordingly, a client-side intercept module and server-side
intercept module according to the present invention may create a
TCP/IP connection between the client-side intercept module 30 and a
server-side intercept module 40 and then multiplex on the TCP/IP
connection plurality of web browser or web server originated
communications while maintaining the TCP/IP connection.
The remaining functions of the client socket manager and the server
socket manager may best be understood with reference to FIGS. 16-1
through 16-4 and FIGS. 17-1 and 17-2 which describe the operations
carried out by the client-side intercept module and the server-side
intercept module when a virtual create, a virtual send, a virtual
receive, a virtual select, a virtual flush, or a virtual close
operation is executed as reflected in flowcharts of FIG. 14 and
FIG. 15. When a virtual create operation is performed, such as
shown in block 333 of FIG. 14 and block 363 of FIG. 15, the
operations beginning with block 400 of FIG. 16-1 are carried out.
The socket manager then determines if a real socket is required as
shown in block 405. If a real socket already exists, such as when
create creates a multiplex virtual socket which is to be connected
to an existing real socket, then the "No" path out of block 405 is
taken and the virtual socket is connected to the real socket as
shown in block 409. If, however, a real socket is required, then
the "Yes" path of block 405 is taken. As seen in block 406, a real
socket is created. The real socket is then added to the event list
as shown in block 408 for monitoring as reflected in block 302 of
FIG. 13. After creating a real socket and establishing a
connection, the virtual socket is then connected to the real socket
as shown in block 409 and create operation is completed as shown in
block 410.
For carrying out the virtual send operation reflected in blocks 334
and 346 of FIG. 14, or blocks 364 and 376 of FIG. 15, the
operations beginning with block 420 of FIG. 16-2 are carried out.
The data is added to the virtual socket queue as shown in block 427
and when complete, the send operation terminates as shown in block
428.
The virtual receive operation reflected in blocks 331 and 341 of
FIG. 14 and blocks 361 and 371 of FIG. 15 are performed by carrying
out the operations beginning at block 430 of FIG. 16-3. As shown in
block 435, the virtual socket queue is evaluated to determine if
any data is present on the virtual socket queue. If data is present
on the virtual socket queue, then the "Yes" path of block 435 is
taken and the data is returned to the function calling the receive
operation as shown in block 436. If there is no data on the virtual
socket queue and the socket is not marked as closing, then the "No"
path of decision block 440 is taken and nothing is returned as
shown in block 441. However, if there is no data on the queue and
the socket is marked as closing, then the "Yes" path of block 440
is taken and the socket is marked closed as shown in block 442 and
the closed socket response is returned to the operation requesting
the receive as shown in block 443.
The virtual select operation carried out in blocks 326 and 336 of
FIG. 14 and block 366 of FIG. 15 is performed by carrying out the
operations beginning with block 445 of FIG. 16-4. As seen in block
446 it is first determined if data or a virtual close operation is
pending for the selected virtual socket. If no data or virtual
close are pending then the "no" path out of block 446 is taken and
the process waits for a virtual event on the selected virtual
socket as reflected in block 447 and terminates after receiving
such an event as reflected in block 448. If data or a virtual close
is pending for the selected virtual socket the a virtual event has
already occurred and the "yes" path out of block 446 is taken and
the process terminates as reflected in block 448.
The virtual flush operation referred to in blocks 335 and 347 of
FIG. 14 and blocks 365 and 377 of FIG. 15 is performed by carrying
out the operations beginning with block 450 of FIG. 17-1. When
called, the virtual flush operation determines if there is any data
in the virtual socket queue to be flushed as reflected in the
decision block 455. If there is no data in the virtual socket
queue, then the flush operation simply terminates and returns to
the calling function as reflected by the "No" path of block 455.
If, however, there is data in the queue, then the "Yes" path of
block 455 is taken and it is determined if the virtual socket queue
is for a multiplex socket as shown in block 460. If it is a
multiplex socket, then the socket header, which consists of three
bytes reflecting a unique identifier for the socket and the amount
of data in the transfer, is added to the real socket buffer as
reflected in block 461. In either case, if it is a multiplex socket
or a simplex socket, the data for the real socket is then moved to
the real socket buffer as shown in block 462. If the real socket
buffer is full, then the "Yes" path of block 465 is taken and the
data from the real socket buffer is sent on the real socket as
shown in block 466. If the real buffer is not full, then the "No"
path of block 465 is taken. The virtual flush function then tests
to determine if there is any other data on any other multiplex
virtual socket queue which is to be sent to the real socket. If the
answer is Yes, then the "yes" path of block 470 is taken and the
data in the real socket buffer is not sent until the virtual flush
operation is called again to flush one of the other virtual socket
queues. If there is no other data or after adding the data from the
other multiplex virtual sockets, then the operation of block 466 is
carried out and the data in the real socket buffer is sent on the
real socket. After all the data in the virtual socket queue
corresponding to the function which called the virtual flush
operation is sent to the real socket, then the virtual flush
operation terminates as reflected in block 467.
The virtual close operation shown in blocks 342 and 348 of FIG. 14
and blocks 372 and 378 of FIG. 15 is carried out by performing the
operations beginning with block 480 of FIG. 17-2. When the virtual
close operation is called, the operation first tests to determine
if the virtual close is of a multiplex virtual socket as reflected
in block 485. If it is a multiplex virtual socket, then the "Yes"
path of block 485 is taken and the "close" operation indicator is
added to the virtual socket queue. Whether the virtual close is of
a multiplex virtual socket or not, the virtual close operation
calls the virtual flush operation as shown in block 487 and then
disconnects from the real socket as shown in block 488. The
operation then tests to see if the virtual close is of a simplex
virtual socket as shown in block 490, and if not, the "No" path is
taken to block 495. Because the close is of a multiplex virtual
socket, block 495 tests to determine if it's the last multiplex
virtual socket and, if it is the last multiplex virtual socket,
sets the multiplex activity timer as shown in block 496. If it is
not the last multiplex virtual socket, then block 496 is
skipped.
Returning to block 490, if the virtual close is of a simplex
virtual socket, then the corresponding real socket is removed from
the event list as shown in block 491 and the real socket is closed
and deleted as shown in block 492. Whether the socket is simplex or
multiplex virtual socket, the virtual socket is marked as closed in
block 497 and the close operation terminates in block 498.
FIG. 13 will now be described as it relates to FIGS. 16-1 through
16-4 and FIGS. 17-1 and 17-2. When a real event occurs, block 302
of FIG. 13 is exited and the socket manager examines the event
based upon how the event was generated. If the event is the timing
out of the multiplex socket activity timer which was set in block
496 of FIG. 17-2, then the path from block 305 to block 312 is
taken in FIG. 13. As shown in FIG. 13, the operations of block 312
and 313 are then carried out by the socket manager to close the
multiplex real socket and delete the multiplex real socket which
corresponds to the socket which connects the client-side intercept
module to the server-side intercept module. The socket manager then
waits for the next real event. This multiplex event timer is reset
by the creation of a multiplex virtual socket as shown in block
322.
If the event occurring on the real socket is a real socket close
such as the web server performing a close operation on the socket
connections between the web server and the server-side intercept
module, then the path from block 305 to block 309 of FIG. 13 is
taken. The socket manager removes the real socket from the real
event list as shown in block 309 and disconnects the virtual socket
or sockets in the case of multiple multiplex sockets from the real
socket or sockets as shown in block 310. The socket manager then
marks the virtual socket as closing and signals a virtual event.
This operation is reflected in block 311 and when all data is
emptied from the virtual socket queue, the virtual socket will
close. After marking the virtual socket as closing, the socket
manager then determines whether or not the real socket, which is to
be closed, is a simplex socket as shown in decision block 315. If
the real socket closing is a simplex socket, then the real socket
is closed and deleted as reflected in block 316. The socket manager
then waits for the next real event as shown in block 302.
If it is not a simplex real socket which is being closed, then the
"No" path of block 315 is taken and the socket manager then waits
for the next real event. Thus, the multiplex real socket or the
socket connecting the client-side intercept module and the
server-side intercept module can only be closed by the timeout of
the multiplex socket activity timer. This allows for the
maintenance of the connection between the client-side intercept
module and the server-side intercept module even after the last
communication between the modules has occurred for a user specified
predetermined time. In the event of a subsequent connection request
from the browser prior to the timing out of the multiplex socket
activity timer, the communication could be carried out without
reestablishing the connection between the client-side intercept
module and the server-side intercept module and thereby eliminating
the need for the overhead of reestablishing such a connection.
The final path to be described of FIG. 13 is when a real event
occurs and the event is the receipt of data on the multiplex real
socket or sockets 36a or 36b in FIG. 12. When data is received on
the multiplex real sockets, this data is examined and in the event
the data includes the close operation indicator such as that added
to a virtual queue in block 486 of FIG. 17-2, then a virtual close
operation is performed and the path from block 320 to block 310 is
taken. The socket manager disconnects from the real socket the
multiplex virtual socket identified in the data received on the
real socket as shown in block 310 and then marks the virtual socket
as "closing" and signals a virtual event as shown in block 311.
Because the close is the close of a multiplex virtual socket, the
"No" path out of block 315 is taken and the socket manager waits
for another real event as shown in block 302.
Through carrying out the operations described in FIGS. 13 through
17 a particular aspect of the present invention establishes a
persistent connection between the first computer and the second
computer over the external communication link. The persistent
connection is maintained until all web browser originated
communications are completed and a plurality of web browser
originated communications are intercepted and multiplexed them onto
the external communication link while the persistent connection is
maintained. The client/server specific data stream may then be
demultiplexed to create a plurality of HTTP data streams and the
plurality of HTTP data streams are provided to the web server. The
persistent connection is also maintained until all web server
originated communications are completed. A plurality of web server
originated communications are intercepted and multiplexed onto the
external communication link while the persistent connection is
maintained. Furthermore, the client/server specific data stream may
be demultiplexed to create a plurality of HTTP data streams and the
plurality of HTTP data streams provided to the web server.
In the drawings and specification, there have been disclosed
typical preferred embodiments of the invention and, although
specific terms are employed, these terms are used in a generic and
descriptive sense only and not for purposes of limitation, the
scope of the invention being set forth in the following claims.
* * * * *